Amazon Marketplace is a much safer alternative to the likes of ebay, and they have strict rules for anyone who wants to sell in order to ensure legitimacy. You'll probably end up paying about the same too, though sometimes more if you somehow get lucky with auctions I suppose. As for payment, Amazon accepts debit cards, credit cards, bank e-checks, and Gift Cards (their own and Visa and Mastercard ones). I've bought a few Tamagotchis off of the Amazon Marketplace recently, including older ones, and have had no issues. Be aware that gift card funds work on ANY order from Amazon, even 3rd party sellers, as Amazon actually pays the seller and you in turn pay Amazon that amount.
Recently, I bought a v4, a v 4.5, and a Tamagotchi P's. I also saw Angels, P1s, and older connection models for sale so you could very well find what you're looking for. All the color tamas are available on the marketplace too. What dazzilitchigirl says is technically correct, as in Amazon doesn't have many older models in stock, 3rd party sellers that work through their site have a good selection, and since they work through Amazon you have the same guarantee.