yeah, im pretty sure, as long as its a qualified leader that is happy to be your mentor then you can do it with them, all they do is sign off what you have done when you have evidence youv done it.
it can even be a family member if you have one in guiding.
my mum was my mentor because she was the only qualified leader in my unit, and that was fine.
also your mentor doesnt have to sign EVERYTHING off, i have other peoples signitures in my book, like other leaders, division comisioners and such.
ask if you can with the unit leader, if not ask your old leader