Where to find Pallet/Skid? [Serious]

I know this will invite Pallet Truck jokes, but I actually need 1-2.

Family member recovering from issues, not full strength and the chair they sit in is a touch too low for them to get out of on their own.

Thinking I can find a pallet or two [preferably not full size, but suppose I can cut to size if need be] to put under the chair and raise it up just enough for them to get their legs under.

Any help would be great.