Warlord Games doesn't just have Black Powder stuff going on this month (though that's sort of the main focus with that Waterloo anniversary-thing going on). They've got plenty of lines with new releases. One of which is Bolt Action. For that, they have the Bishop Self-Propelled Gun, because nobody likes having to push or carry their gun around if they can instead get it to do that work itself. And considering the size of this gun, trying to just push it where you want wouldn't be too feasible anyway.
This British vehicle was based on the Valentine tank... to which they just sorta put a box on top of it with a gun sticking out the front. Hey, sometimes simple is more practical. It's a weapon of war. It doesn't have to look pretty if it doesn't want to. Unfortunately, the box top limited the gun's elevation, so it couldn't really shoot too effectively. So the crews would build earthen ramps to lift up the front of the gun.
The Bishop saw wide use in North Africa and into Italy. Now one can be yours (well, a model of one) from the Warlord Games Webshop.