Unbranded tablets on amazon seem to sell for £50, you could probably find some from a shop that price (just make sure they run android) and then you can airgap with electrum without buying something more specific/expensive.
A lot of hardware wallets (like the trezor and ledger) do have signature verification built into them though, which makes them seem quite a bit more secure.
Have to be careful with buying online with hardware wallets, some fuckers just can't stop stealing from people by tampering the wallets and then stealing the funds from those people that have bought the tampered wallet. I myself bought a Trezor, pretty nice hardware wallet and it's easy to use although I don't have a lot to store in it though.