Are you sure you can't contact them?
It's annoyingly tricky sometimes, but you should be able to. If there's no 'contact seller' option associated with the item, click the seller's name then go 'send a PM' (or 'contact seller' or something similar) once in the seller's profile.
Also make sure that they do open the bidding up to you, and they don't just say they will. I recently lost an auction I really wanted because, despite assurances I could bid, etc. the seller never gave me permission. Damn I hate eBay's set up sometimes.
Make sure to ask how much postage will be though, and that they DON'T use FedEx. I've had sellers be vague, saying they'd send things the 'cheapest way possible'. Fully insured and tracked FedEx on a $10 item to Australia is simply ridiculous, especially when the only times I've had problems receiving things from regular US post I'm pretty sure the problem was earlier in the line than the post office...