im in a different country/continent. So can’t help you with rootstocks.
here we usualy graft apricots on prunus domestica / insitia rootstocks.
So if you can’t score some rootstocks and have a EU plum nearby. You coult try and graft it to that.
You have a slight chance of introducing viruses and diseases though. Not unreasonable large in my gues. But it wanted to say it anyway just to be complete.
You could also look at this topic
for other possible rootstocks or compatible hosts.