Just so that you're clear, there is no single gear that makes reverse in these transmissions. Instead, the same two gears that are used to make first, second and third is also used for reverse. This is the "magic" of planetary gear systems, and the basis for most automobile automatic transmissions.
There is a website (makcotransmissionparts.com) that has exploded drawings of your transmission. The drawings can help you see what parts your transmission contains.
If the valve body can be serviced without removing the transmission (and the work is reasonably priced), the I'd consider repairing the valvebody without servicing the reverse clutch. However, if the transmission must be removed to service the valvebody, then it is probably worth the incremental expense of a complete overhaul. I will depend on the cost of qualified labor verses the cost of the parts.
I don't know of any companies that ship parts to your country. Have you checked for online companies that serve international companies?