I have produced a range of Static Caravan kits in OO-scale because the ONLY alternative models currently available are from Bachmann, at £25 each!. Here are three different 'vans, with one being available also as a customisable layered file with alternative colours and fittings.
Available from https://www.modelrailwayscenery.com/building-kits/ in OO, N and O-scales.