i worked through the decade or so when modem speeds were increasing two to four fold every year which ultimately made hundreds of models outdated in a very short time and though the modem itself would often be tossed, i hung on to dozens of modular power supplies with various voltage (ac and dc) and wattages. in town there are also a couple of used electronic supply outlets where i can find bins of similar power supplies.
when it comes to running just about any accessory, there is definitely a sweet spot narrow voltage range that i typically first find with a variable transformer but then look and often find a modular power supply that will act as the dedicated power supply for that accessory. unlike a common accessory bus, the target accessory will see its perfect operating voltage without the possible drops which might occur with a common accessory bus feed.
cheers...gary