or maybe this is better:
This is from a thread I found:
here it is again, I ordered mine several weeks ago, the correct bulb for 10 bucks and free shipping.
IF ANYONE WANTS TO KNOW HOW TO ORDER THE TCP 19/85W BULB FOR 9.99 EASILY THEN LISTEN UP!!
ok,
step 1: Call the home depot supply number 1-800-431-3000
step 2: Ask for the special order department, the bulb can only be special ordered.
step 3: the part # for the bulb is 99570, this is for the 19w 5100k par 38 TCP bulb, I assume the 16w is also available, but you will have to ask them to look up its part number
I had to create a special order account, it was free and fast to set up, also the bulb is only special order so it can't be ordered online through the HD supply catalog. Shipping was free and it should take 6 to 10 days.
This is the cheapest place I have found to order the correct 5100k bulb!