If you're not going to restock it, you might want to get the late style convertible buttplates, as used by competitive shooters. These are aluminum, and are adjustable for height, and angle. The hook is a single, and easily detached for benchrest use. 
I think you might try Brownells for this item. My Win. 52 has one of these plates, and it's very comfortable, and easy to use.
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Nope rafter7, it's a Canjar ball and it fits into the mag well of the 52. It's adjustable for height and angle. This was my latest find at a local gun show! A whopping $20! I've got the original 52 stock also, but I like the custom better!

I'll take it apart and see if I can find a maker. Or call a friend who shoots competitively, and see where he get's his.

Thanks 4227! It is a Freeland. I had to remove it from the gun to find the marking. It wasn't on either plate, but under the adjustable base.

Marlinguy

Any chance we could get some pics of that Canjar ball ?  detail of how it goes in and adjust etc. Ball shape too.

For some unknown reason I have been making a couple of new palm rest for my CPA.  I like CPA's Scoyen the best but have 3 or 4 different ones now. Hand shaped, turned etc. Firend of mine put a Billiard ball on one of my bases. Looks good but is pretty small for a heavy rifle.

In Brophys Springfield book there are a couple of 03's set up as free rifles. One has the palm rest attached through the magazine like your Canjar.

Boats

4227,

you say you got a lot of mark III ammo could you spare a brick? i am also a rimfire shooter 

welcome to ASSRA 

4227 would that be like IMR 4227 i try and change loads over to it because i like how clean it burns its wonderful in a 38-55 but not as accurate as 3031 but close

rafter-7

CPA makes a freeland style stock for the Martini International.

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4227, 
 
you say you got a lot of mark III ammo could you spare a brick? i am also a rimfire shooter   
 
welcome to ASSRA   
 
4227 would that be like IMR 4227 i try and change loads over to it because i like how clean it burns its wonderful in a 38-55 but not as accurate as 3031 but close 
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rafter-7    \Well I don't know if I want to get rid of any MK III or not but if you want to post your e-mail address I can contact you about the subject.
As far as :4227" goes, yes that would be IMR 4227 or the "Old Schuetzen" can etc. I have tried many powders over the yeards and have found that the "Old Timers" pretty well knew that they were doing and as long as we stick to trying to equal or pass what they were doing and in the manner they did it, IMR 4227 is the way to go. The "new" actions, stocking, methods etc. then all bets are off. It's TRADITION!!
As far as the .38-55 etc. goes, at the end of a long day shooting you will be whipped with the larger caliber unless your built like "Hugs & Kisses"! I shot a .38 M.L. Schuetzen because we discovered that any caliber below .38 presented too many other problems with fouling etc. You seldom see any M.L. schuetzens below .38 (>380) cal. 
In what pwrt of the country are you located?
Regards, 4227