High chair replacement pads and covers are available from Diapers.com and BuyBuyBaby.com, as of 2015. It is also possible to buy replacement pads directly from manufacturers such as Fisher-Price.
Diapers.com sells a number of high chair replacement pads and covers from several manufacturers including OXO and Stokke. All of the products on the site feature reviews from buyers, and many items have videos showing how to use them. Diapers.com also features free shipping for orders over $49, as of 2015.
BuyBuyBaby.com has a number of high chair replacement pads from brands such as Balboa, SpecialTex, Sven and LeachCo. Reviews are available for many of these items, and the items are searchable by price, popularity and rating.