Hi Ward, I'm just undertaking exactly the same project, here in the UK.
I have an original paint and interior catalogue which lists the standard seat covers for all P15 convertibles as red leather with bedford cord.
I've attached a scan. The leathers have changed color with age, so please don't match to this.
As you can see, tan leather with cord, or blue leather with cord were also available as options.
In addition, I have seen period pictures showing two-tone cord (which I think my car had originally) and all leather.
The red is a very deep color - maroon is probably an accurate description. Some people describe the color as mulberry.
Bill Hirsch (HirschAuto.com) stocks bedford cord fabric. He also has very good matches for the vinyl. He'll send samples.
Leather is available in a wide range of colors, so you will be able to get what you want.
Sorry I can't help with a top release handle. Good luck with that.
Please stay in touch.
My email is Robin@RockTheJoint.com
Also attached a couple of other pictures of original interiors.