Currently, the only known (by me) breeding group outside of Tanzania is in Belgium. The chances of Tanzania reopening for export are unpredictable, but those of us watching it are not holding our breath. Most likely, you have a lot of time to put all the cage and stuff together before they find their way back to our shores.
There is a quiet merumontanus fan club that is keeping in close contact with the European connection (Jurgen) and we'll work on details if the opportunity arises to bring a shipment over.
There have been a number of Jacksonii jacksonii sold as merumontanus lately (for reasons unknown - they weren't charging meru prices), but that won't work for you because you know the difference. So your knowledge is working against your happiness. That is what you get for knowing stuff.