Or go to REI or a shoe store and get a pair of Superfeet insoles. About $35. Wear them in ALL your shoes, ALL the time to support and sort-of retrain your feet.

Since you'd be doing a lot of biking, I'd recommend the Berry with the metatarsal arch support for the forefoot. (you'll be putting a lot of pressure thru the forefoot on the pedal)

If you have a really good shoestore, they should be able to "post" a 2nd pair of insoles (if you find some you like) specifically for biking, but start off with one pair in all your shoes and see how it goes. And if you don't like them you can return them to REI. (or sell 'em to me, if you're a size 9.5 )