Haven’t found something yet. I am currently try to find more informations of the belt mount in the handy discord as mentioned by @Abdulis here https://discuss.eroscripts.com/t/diy-handy-hands-free-ideas/3669/116?u=andymaniac
His setup looks more stable and he has some pictures in the discord as well:
https://discord.com/channels/699664632444616794/773186024963702815/1031505313297350717