Here's a guide made by roujo and I think yutsi may have been the first to do this https://roujo.toepi.moe/dance/bar-building-guide This is what the LTEK bros in the stamina scene seem to do.
Keep in mind, a bar is essentially a giant lever so to make one that doesn't wobble or break is actually a very difficult job. Whatever homemade bar you make, unless it has a bunch of triangles built in, I'd treat it with some care and expect it to wobble a bit.
Personally, I don't know anyone who has done this and I'm not 100% if the dimensions would work out, but something like the Booty Kicker ™ seems like it could work https://www.amazon.com/Booty-Kicker-Exercise-Portable-Exercises/dp/B089N3CKGZ/r