who can make custom timing chains?

i have a friend who is building a 74 Yamaha DT400 enduro motorcycle.

he was talking about upgrading to a SC500 motor to replace the 400.
he was complaining to me that the balance shaft chain is made out of unobtainum. replacement parts are not available anywhere.
he was telling me people were building these motors without the balance shafts. the problem is they vibrate badly when you do this. it also keeps the RPM's down so you really don't gain as much HP as you could if it had balance shafts.
the chain is the same between the SC500, MX360 and MX250 motors if it matters.
the chain looks like a regular double roller timing chain to me.
there is a lot of knowledge on this board. does anyone know of someone that could do something like this?

THANKS for any replies or ideas in advance.

Kaplan Cycles rebuilds old dirt bikes so maybe they might know.

https://www.kaplancycles.com/

Most chains are a Borg Warner chain in almost any timing set. Maybe see if they offer one for your application.

Check Tsubaki's website. They probably built the chain to start with.