Try to find a local dealer who will agree to selling at spot plus $2 or 2.50 and buy at $2 under spot, that give him a $4 hedge and you won’t have to pay shipping and insurance.
If there is a mine/refinery in your area you may be able to buy at $1.50 over spot and sell at $1.50 under spot.
If you must buy online try www.Kitco.com or www.apmex.com But buying local or from a mine/refinery is really your best bet.
Keep in mind, silver coins are not .999 fine, for instance a Morgan silver dollar is .77 of the one ounce price. A good melt calculator is found at: http://www.coinflation.com/coins/silver_coin_calculator.html
Hope that helps, by the way, with silver under $20 an ounce, this would seem to be a great time to buy.
Those premiums are large. Provident will sell you private mint 10oz bars at slightly over a buck/oz premium. Or 1 oz coins on occasion. To me bullion is bullion. Get it cheap, lay it away, and hope you never need to sell it. But I like gold better.
In a true SHTF situation .22lr is probably worth its weight in silver anyway.