Another option for you martin is to get yours repaired and your 31A-10 is listed here.
https://uk.carmo-electronics.com/repair/ecu-tci-cdi-box/caru-ya-xj900f-spark-unit-tid14-37-58l-10-tid14-19-31a-10?___store=carmouk_store_en&___from_store=base_store_en
ahhh, this might be of interest....
There is a company in Oz that lists a replacement for your TID14-19 (31A-10)
https://www.ecureplacement.com.au/ecu-product/yamaha-xj900rk-seca-tid14-19-ecu-replacement/
and a different listing for the TID14-37 (58L-10)
https://www.cdireplacement.com/cdi-products/yamaha-xj900-tid14-37-cdi-replacement/
However, they are both the same price and it may be the same unit? I note the model number listed 000.299.000 S120 45 is the same on both entries.
I can see its not cheap, but it may be useful in finding one closer to home
or an email to them might be useful to you.
NE0's post in XJ900F 58L TCI compatible with XJ900F 31A? was marked as the answer