Hello:

As you mention you can remove the upholstery yourself, your best bet
would be to do that and then buy enough at a supplier to recover the
seat--and then take it to a friendly neighborhood shoe and leather
repair place in your neighborhood. Give them the old seat covering and
the new material and ask how much they will charge.

I did that for a seat cushion repair on a 240 of mine recently and
they charged me $20 and did a great job.

An auto upholstery shop might not be willing to do this as they count
on the labor for removing the old material and doing a bit of markup
on the materials--as they need to if they are to remain in business.

Still, you never know and may wish to ask them or a local upholstery
shop not necessarily auto related  if they will do the sewing.

I suppose much of this depends on where you live and the availability
of craftspeople.

In my case, the owner of the shoe repair shop was pleased to do it as
he has repaired shoes for me and likes my dog (who always comes with
me to the shop.) He did say he'd have to look at the leather before he
agreed to do the job, but was pleased with what I brought.

Good Luck

Doc