You can get items recharged by particular mages in mage guilds - this costs money (quite a bit I think), obviously. You can also recharge them yourself with stones you find in Ayleid ruins (Vargas or something?). I think they are the only ways?
I don't think it's worth buying a new horse - unless you plan to manually ride everywhere, in which case you might want to buy a faster one, if you fast travel then it's not worth it at all.
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