Solana items are paid for in the currency the listing uses, from a Solana wallet. Most listings use SOL, and some collections use USDC on Solana.
A cross-chain buy, where you pay with almost any token or from another network and OpenSea converts it for you during checkout, works for Ethereum items but is not available for Solana items yet. A Solana purchase settles in a single Solana transaction, so the payment has to already be in the listing's currency in a Solana wallet. It works in the other direction, though: you can pay for an Ethereum item with Solana funds.
If your funds are elsewhere, you do not need an outside bridge. You can swap to SOL in your OpenSea wallet, including from another chain in the same flow. The swap options you see depend on the route available at the time.