I have a load of thick jigsaw mats covered with a vinyl sheet. There are wooden batons all around the edge, nailed down to the floor. That both holds the mats in place, plus the vinyl cover is stretched under the batons so that stays put too (it's a pain to get it stretched though, you need a load of people pulling at the same time all around the sheet).

This vid from a while back shows how they look at my place - https://www.instagram.com[...]Aw3TjACZr/

Thanks Can. Looks good.
Do you need to tighten the vinyl every now and then, or is it nailed in place and can’t rip?
I’ve seen companies like “Vennekel” produce tailored stuff, but I think the price is very high.
Where can I get such vinyl?
Cheers

So far, there hasn't been a need to tighten, though it's only been in place for about 2 years at this point. Though for a lot of that the gym has been closed, due to covid this year. Also, this vinyl was previously in use for several years by another BJJ club that used to rent the same space.

The main problem I've had is that it appears to be difficult to get such a large piece of vinyl without seams to join multiple bits together. There are therefore are weak points where it joins that eventually can start to fray. It's also a real pain if you ever want to expand the mat space (which I did), as then you have to somehow combine the new piece of vinyl with the old one. I tried all sorts of methods (e.g., heat gun), but eventually had to go with the crappy option of just whacking a load of gorilla tape on the join.

I can't actually remember the name of the place I got it, as I went through the landlord of the space I rent (he included his old mats and vinyl as part of the deal when I initially started renting from him, so I just paid him to get me some more when I wanted to expand). However, it was a local UK company, so possibly not ideal for your purposes in Belgium (especially with the massive shitshow about to hit with Brexit in January ;) ).