Dinette Cushions

My wife did ours. We bought "quality" foam and she made new zipper covers with upolstrey fabric of our choice. One thing to keep in mind is don't get foam that is too thick as you won't have the clearance between the top of your legs and the bottom of the table. Gives you the chance to truly make your RV to your personal taste!
Brian

Regarding the cracking vinyl,

That has been a problem introduced into the RV industry soon after the recession of 2008/2009 when the supplier of much of the vinyl fabric material switched to China-sourced material. It breaks down similarly to those leather couches being sold that have 15-25% of leather impregnated into the vinyl.

Foam is expensive, plan to do this once, use quality foam that won't break down. Its a pain to do it yourself, I would have it made to order.

some rv people have used:

https://www.thefoamfactory.com/

https://www.cushionsource.com/catalog/rv-cushions

Here is some reading to see what others have experienced:
these are older threads so the prices are off.
Its said to not use more than XL 38 foam otherwise its too hard a foam.
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/23411753/print/true.cfm

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27777972/print/true.cfm

Any upholstery shop can do it easily. Or go to a fabric store and see if they have a bulletin board with names of people who sew.