Not so fast on condemning urethane drive belts.... They are the new IT thing: They are the material of choice for industrial conveyance systems, CNC, and robotics.
I suggest you look them up on Amazon in a 10mm-12mm round stock, and buy a 10’ length so you can make a few Belts. The DIY method is very simple and very quick:
1) Cut the ends squarely to the correct length with a utility knife
2) Clean a putty knife with solvent(s) to remove any residues/contaminants
3) Heat the putty knife to red hot, and press it between both ends of the belt long enough to melt the urethane
4) Immediately press the ends of the belt together and hold until cooled enough to stay put. This welds the ends together. Done.
These are very strong, very resilient, very long lasting, and super smooth operating. Plus they look very perky in those candy colors 😁.
There are roughened surface or smooth surface stock. The roughened version is supposed to be more resistant to nicks and cuts. The material is supposed to be stretched a bit, I don’t know how much, but some tension is needed, so your hinged motor Mount should be ideal.