It is strange that OFA customer support said they have no upgrade for this device. They have an amazing library of upgrades and more amazing data on which models need which upgrades. Your device must be fairly common (given its several previous mentions in the various remote control groups).

I expect OFA does have the right upgrade and you just got one of the less skilled support people there.

If they didn't have the upgrade, they have at least one employee who knows how to get upgrades from the JP1 site (though I think it is quite rare for them to do so).

Doing it yourself with JP1 is easier and better (once you have the cable and a JP1 capable remote) but if you really didn't want to buy another 6131 for this, you might try again to convince OFA customer support to install the upgrade.