I'm not sure I can help you find a place to buy grapes. The state of Idaho places limits on where grapes can be brought in from. Due to certain pests like the grape phylloxera, these limits are very strict. You can contact the Idaho State Dept. of Agriculture for more information on getting grapes vines. You might also contact your Ada County Extension Office for help.

There are many grapes which are hardy enough to survive Boise winters. The greater limitation is whether there is sufficient heat in the summer to ripen the fruit. This publication can help with that information.

Here is a link that might be useful: Growing grapes in Idaho