Mismeasured flooring quote

Hi all, we have an issue with a flooring company and just wondering if anyone has had something similar happen or has any advice.
We had vinyl plank flooring installed 6 months ago prior to moving into our house. We knew we would be renovating the kitchen soon so didnt get the flooring installed in there but had the product ordered and paid for to finish this area of floor when we were ready. I have emails that clearly say the quote and invoice we got included product only for the kitchen area.
It has taken us a bit longer than expected to get to the kitchen reno but as it is now only a month away we thought we best check the boxes of planks we have for the kitchen and make sure there is enough etc. Lucky we did as there is not enough and we need another box or possibly 2.
I called the flooring shop to order these and was given an outrageous price for 2 boxes of planks with the explanation being that being such a small order the price includes freight from the supplier. The price works out quite a lot more per sq metre for product only than we paid fully installed on the original job.
Am I wrong in thinking that this was their mistake, not ordering enough originally and if the quote and invoice I have include product for kitchen then they should supply the right amount? They measured the house and kitchen and if they have made an error it should be on them?
We wouldnt mind paying for the additional planks but at the price we were originally quoted and paid not double because the floor shop "cant absorb the freight cost on small orders".
If anyone has any advice, I'd appreciate it before I take on the floor shop.

Since you have the boxes you know exactly what the product is. Put searches into eBay, Gumtree and Facebook Marketplace to see what comes up. Often, excess stock from renovations and builds come up. Just be sure to check if there is a batch number, as colours may vary if the product is made in batches. You can also ring around other suppliers to see if they will order for you without a small order penalty. Finally, if you really want to go with the original supplier, write them a letter outlining your concerns and proposed solution. Then, if they refuse or do not reply, you will have documentation and may be able to make an application to the fair trading organisation in your State.

Thanks for the reply arcadelt. First thing I did was jump on Gumtree and Ebay but no luck.
The product is exclusive to this particular chain or flooring stores so cant source it elsewhere. We are in a regional area so I called a metro store and they told me they also have high freight costs on small orders so would be no use trying that avenue either.
Just waiting to hear back from the store and hoping they will compromise on the price or I will be calling Fair Trading.

The problem you face could be a tricky one.
When the flooring was originally laid, if the people laying the floor weren't told that so many boxes of planks was for another area, they could have been a flippant with wastage and a lot of cut ones could have been thrown away.
I know that when our tiles were laid, we thought that there would be a lot left over, but I think I counted 5. A whole box was thrown in the bin as it much have been dropped and then there are nearly whole ones in the bin as wastage.f

The installer definitely knew there was meant to be enough left for the kitchen.
Anyway we have had a win... after a few phone calls with staff who were full of their well used excuses I went in to see the manager. Face to face, I told him it was simple, we had an agreed install and supply and price and they had not met their end of the agreement. He agreed with me and we are getting the additional planks free of charge.
Glad we got the right outcome but makes me so mad that they try and pull this s#%t on people. Will not be doing business with them again.

The installer definitely knew there was meant to be enough left for the kitchen.
Anyway we have had a win... after a few phone calls with staff who were full of their well used excuses I went in to see the manager. Face to face, I told him it was simple, we had an agreed install and supply and price and they had not met their end of the agreement. He agreed with me and we are getting the additional planks free of charge.
Glad we got the right outcome but makes me so mad that they try and pull this s#%t on people. Will not be doing business with them again.

Where abouts are you based in kld?