We know of a number of companies that do offer this service including flexiprint in Albury. I believe the cost is dependant on the numbers you want printed, the type of plasticol print (ie with adhesive beads or not), and also whether you are going to press them yourself or not.
We have gone through this process over the past year, so know where you are coming from.
With regards to TShirts and where to buy it all depends on the quality you want and the end price you wish to charge. We tend to use Shiny shirts as they have a range of styles one is similar to bonds and a customer of ours requested it.