The Problem with Leman Russ

I bought a second-hand Leman Russ tank which arrived just before Christmas. Like a kiddy on Xmas, I started assembling my new toy over the holidays, and discovered to my disappointment, that the side panel of the hull is missing, as well as parts of the two sponsons. Seems the previous owner had given it a bit of kit bashing and made a mess out of it, as well as losing some of the parts. The sponsons I'm not too bothered about, as I can buy the weapons sprues from Games Workshop with the sponson parts on them, or substitute some Baneblade ones, which should at least make the tank look a bit different. The real problem is trying to get ahold of the outside hull piece. You can't buy the outside hull sprue (ironically though you can get the Leman Russ Accessory Sprue which has the main body parts on it). I tried the local store today, and while they were very helpful, they didn't have the part i needed. Looks like i'm going to have to try scratch-building a replacement part. The actual part isn't too complicated in terms of it's shape, but it's more the outside detailing that could get a bit hairy. I'm thinking I build the basic shapes out of plasticard, then pull some moulds of the various components that go on the side wall and make some parts to attach to detail it. I'll let you know how it goes.