MMD's many PMX models, mostly free, may be manipulated using free PMX Editor, exported to OBJ+texture-calling MTL using its tools.

Downside is many have material and texture names in eg Japanese. Free version of Bandizip can extract sense rather than dipthong soup, while Google Translate lets you copy/paste names.

Although PMX uses a 'LH' coordinate system rather than eg OBJ's 'RH', there's a mirror command. Of course, if item is not 'handed', that's even easier...

Figures lose their 'bones' if exported to OBJ. I've not yet found a way around that...

Props often have dials to turn, doors to swing, ramps to drop etc etc. Yet, I could not find a way to operate such then export the result. Today, serendipity struck !!

This model came with a lower-poly 'dummy' door+frame, plus one whose default closed door can be swung per the 'preview'. Have managed to set door 'ajar', export it.

When I've figured how to do it repeatedly and to order, I'll do a brief tutorial...