If you are actually a practising designer most paper houses (GF SMITH, Robert Horne, Fedrigoni etc.) will happily send you out their sample books and will send out samples if you are working on 'live' projects.
I would suggest that you continue to ask the printer for the paper samples, they afterall should have relationships with all the major merchants (if they are any good) especially if the the sales rep is any good he can advise you about what sheets print well and which don't and also less costly alternatives especially when you have a client that falls in love with a GF Smith sheet.
they might like the feel but they definately wont like the price.
Obviously your printers will only be happy to provide this service to you, if you are are either placing work with them or refering your clients to them when the time comes for the job to be printed.