One thing for sure, you will not be able to perform it at your gig this weekend.
Jags. With the greatest respect in the world. I believe he means that if you buy it now there is no way that you should be performing it tmw., and I am sorry but I have to agree with him on that.
Magic is an art, and as such deserves practice. To buy an effect that requires any sleight of hand, and then to perform it for a paying public the next day is (imho) taking the micky out of the art a little. You won't just be doing yourself a diservice, you will be doing any future magicians that these people may see a diservice.
Everyone is rooting for you for your gig, but seriously you should have been thinking about this months ago, and certainly not be looking to buy anything new to perform with just a days practice.
You seem to be under the illusion that all magic is selfworking and can be performed straight out of the packet, and in my mind, even self working magic requires a lot of practice....
I hope you don't take this the wrong way, as I am trying to give what I believe to be helpful constructive comments and not just criticism, but you are starting to scare me...
And out of interest, The trick you described, is more of a sleight that uses three silks. It is also commonly seen with sponge balls (even sponge banana's), but when done with silks it often ends in a silk fountain. The sleight isn't particularly difficult, but to make the whole thing magical without exposing any method takes a good deal of practice.