Welcome to SaleHoo! :)
The products are customized by this company in partnership with Swarovski and the brand name electronics. I donâ€™t think you can source them from anywhere else, than from this store that you have found, as this is a highly specialized service, and the specific products you need requires a pre-order, to be customized. No one will Swarovski crystallize musical instruments without a sure buyer. You may however find wholesale suppliers and drop shippers for Swarovski crystals.
There are several tools that will help you find out if an item sells, but high popularity of the product does not mean it will be the easiest to sell. You need to assess, do you have a lot of competition? Can you offer better pricing to succeed? Promoting your store or auction listing also plays a big part in the selling process, and you need to efficiently direct your marketing efforts to your target customers.
A good point in your side at this moment is that you appear to have decided on a niche, and better if you are very interested in your product line. :) If you think there will be a high demand for Swarovski crystallized musical instruments in the market you will be selling to, and Link hidden: Login to view will not be easily available to them, then you may try getting in touch with that company and propose a dropshipping arrangement. :)