If you want to stick with a roto-start like backplate I'm sure you could find something that fits both your engine and is operational once it's fitted into the Savage.
Most of the time older Savages (non XL) want a roto-start that has the drive in the corner and not in the center of the rotoplate. So while A-Main suggests the following for a Mach 28, even if it fits your Mach 26, I'm not sure that it would work on your Savage.
http://www.amainhobbies.com/product...haft-Start-Back-Plate-for-Force-Picco-Engines
Never used a Thunder Tiger starter, but they market this for the Mach 26.
http://cgi.ebay.com/Sullivan-Tiger-...Control_Parts_Accessories&hash=item483a87387f
If you have a good LHS, you might want to take the engine there and see if they have something that works.