You can buy cheap cassette players new, they probably wont have dolby etc. but are noise tapes made using this? I use one and find it OK. As for Ebay, if the seller says it's in good working condition (and they have good feedback) you should be OK, and if not be able to get your money back. Though 'antique' walkman's are not cheap!.
edit: If you do get an old machine check out head cleaning on youtube...