Magic Tricks

Acknowledging that this question is over a year old, I'm hoping that you've found your solution.
Just thinking out loud, but these answers for "big" coins refer to Kennedy halves, Eisenhower dollars, Morgan dollars etc. Real coins with high coin values (as coins go).
Is that what you mean? Big as big value coins?
OR, big as in size? For example, the 3" gimmick coins. They seem to be showing up a lot lately. There are some 7" available too. Even 10" also. These can be costly too, but there are many cheap ones available. No need for perfection as with the smaller imposter coins because, obviously, these are not real. Never meant to be eh?
Just wondering?

To find Eisenhowers, I went to a bank (you may have to go to multiple) and asked if they had any. There, you can exchange a dollar bill for a dollar coin, or two half-dollars. I also gave them my number in case they came across more, and a couple weeks later they got more coins then I could fit in my pockets... So I gave them a $20 and walked out a happy man.

As girspiggy states, Silver coins (such as Morgans or Peace Dollars) can get fairly pricey, and if you ever care to start using gaffs (which are fun to play with as well as perform!), they're going to cost you over $100 for a single expanded shell. Penguin Magic has Expanded Shells for Eisenhower coins for about $60, which is less than half the price that I've seen Morgan Shells go for (and in some cases, 1/3rd!).

So I definitely recommend Eisenhowers for beginners, they're still big and shiny :) Morgan Dollars are more like Eye-Candy, since they do the same thing, but cost more. Also, if you have an urge to be unique and some paper-money burning a hole in your pocket, you can aim for Peace Dollars. Less expensive than Morgans, but gimmicks would have to be made custom by the few craftsmen that do coin-gaffs, so gimmicks will probably be a lot more expensive.

While Penguin is by far my go-to magic source, I'm often successful on eBay in finding items that our out-of-production or that Penguin doesn't stock.

And third place to Penguin and eBay is live auctions, which I freqently regularly as my "other job," is as an eBay seller. Live auctions are hit or miss, as you will rarely find something you're looking for. But I can't count the times I've picked up something for cheap, thinking, "I can do something magical with this!"

You should probably consider silver dollars for your coin magic! Eisenhower dollars are easy to find. Others use Morgan silver dollars which can be found in coin shops and online. Keep in mind they can get a little expensive. We also sell fake versions here which look super great but don't break the bank.