Toy army men cannons may have some utility.
I based my lascannons on such carriages. They were large at the time, but are probably exactly the size you need.
They are soft plastic, so clean well and prime with Krylon Fusion spray paints.
Toy Soldier company has them insanely overpriced at 14 each.
https://www.toysoldierco.com/Plastic-Toy-Soldiers/Plastic-Toy-Soldiers/Unpainted-Plastic/WWII-Field-Gun/Product.aspx?ProductID=7416&DeptID=6&&
The come in and out of stock at Amazon periodically for a tiny fraction of that. If you can't find anything, look for 1/48 kits for howitzers, field guns and light artillery.
Automatically Appended Next Post: One more out-there idea. The turrets pictured here are "Final Faction
AT-4" turrets from Dollar tree. Too tall, but perhaps could be cut down to make low quadriped gun carriages?
Price is certainly right