find a friend or neighbor with a band saw and have them cut them for you…

You don’t state why they wouldn’t cut them. Was it because their machine was down? If that’s the case I would call nearest location of that store chain to see if they have a working cutter. Unless the competitor sells the exact brand of blind, they won’t cut the blind for you. The reason why is that if they make a mistake in cutting, they cannot replace that blind.
Although there is a recommendation to cut them yourself, I would highly recommend the outside mount as suggested by another poster.

I had the same problem with mine. I know what you mean buy the expense of custom blinds. I solved my problem by mounting them on the outside instead of having them inset. At first I thought I wouldn’t be happy with the look but I actually like them better.

you know any one with a table saw if so bind the blinds tight and have someone cut them for you but you will need to go get a blade for them and tell them to cut slow then just treat the ends to a good sanding and some stain to match and some spray on sealant