Sounds like a Vintage Modified Jazz. Is this it?
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I've never even picked one up to try, let alone own and modify. (the natural maple look really isn't my thing)
Here's a couple of possibilities;
1. Remove the guard, trace it out EXACTLY (include the screw holes) onto graph paper and take it to a music store that stocks replacement pickguards. Hold it up to what they've got and see if it's a close match. If I remember correctly, the guards with the notch in the neck pocket are for the American-made Fenders. I suspect the standard MIM's would be a bit closer, but don't hold me to that.
2. I've recently been looking into having a custom-made pickguard and have found a number of places that stock a variety of types. Some of them will even reproduce it with a new color scheme. You just have to mail your original to them (x2 the shipping, though).
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www.terrapinguitars.com
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…just to name a few.
If you can't get a solid confirmation on "this fits that" from here, but don't want to buy one that "almost, but not quite, fits", give some of them a call.