There are three systems involved:
(a) the shape of the mechanical key
(b) the RFID system that determines if your key can *start* the Sprinter
(c) the RKE (remote key entry) system that handles the door locks
The frequencies used by (c) are country-specific. Different countries allow different radio bands for those functions. (the US is 315 MHz,.. it's listed on the datacard)
In the US, you can overcome (b) by two means: (1) have a locksmith "clone" your existing key... he would have a device that listens to your original key and recreates that radio pattern in the new key. MB does not do that, but 3rd-party locksmiths can and do.
(2) you can hide your original key near the RFID antenna in the Sprinter, and then just use mechanical keys (without RFID chips).
That makes you van easier to steal, but gets around the "can not get new RFID keys" problem.
A good locksmith in the US could create an (a) and (b) "clone"... they do not need the Sprinter, but they do need your existing key.
A "clone" key appears to *be* your existing key to the Sprinter, so it does not require a re-programming of the Sprinter itself.
MB creates *new* keys, which do require reprogramming. MB dealerships do not create "clones".
I would start by finding a locksmith who can copy/cut new (a) mechanical keys... it won't be able to *start* the Sprinter, but it will be able to unlock the doors. You can also ask if they can clone the RFID chips.. you might be able to achieve an (a/b) key.
The other way to go is to replace (or reprogram) the ECU and SKREEM (or NCV3 equivalent) with ones that will accept keys designed for the Ukraine.
good luck
--dick