If you like the Mk1 Shoebox Pattern (which I do), they show up on ebay now and then for relatively cheap. You could probably collect a bunch over time.

Can't make promises for 31 though

edit: could try converting them from Rhinos or Land Raiders too. They're surprisingly small.

You have 3rd editon at the front, late 2nd edition  in the middle and forgeworld bfg at the back!

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