Yes. You can buy rare candies in the battle frontier for 48 bp.
No there isn't BonsAi*. Rare Candys cannot be bought but can be found scattered around in Platinum. Heres a link to there locations.
Rare Candy Locations
Hope this helps :)
How to change your username How to add a user avatar Why was my post hidden? The points system Question etiquette Flags vs Downvotes Anime FAQ
Type a Pokemon name, type, move or ability to see instant results.