I guess starting to pay 100EUR/mo. *now* means that within 3-4 months, the down payment is enough to guarantee you a NeoN board; and after another 6 months the full purchase price is paid off, perhaps in time for it starting to ship. Less if you've already donated.

Any distributor could offer to rent or resell some devices like a commercial phone contract. But 45EUR x 24months would only cover the unit cost of a handset, whereas they'd be looking to make a healthy profit and insure against returns under warranty (including fraudulent cases due to owner negligence) and their handling costs. It'd surely cost more than 100EUR/mo. with all that factored in, so no better than my suggestion above.