I just visited the Webench for National. Apparently, it will not do a complete design for the LM2577. Maybe it is older, or just not included for other reasons. If you enter your design criteria, which I guessed as being 5 V in , 12 V out, and 800 mA, you will get a set of possibilities. I picked one of the cheapest, the LM2700MT-adj. For that device, National gives the complete design, including part numbers and vendors. Most important, you can buy the complete BOM from National for $4.14, excluding the PCB. A generic PCB is also available. I didn't price that out. All told, you can probably get the whole thing, including PCB, for around $25 or less. At least, that is what it cost me last year when I ordered a switching supply. It is one click ordering.
The nice thing about the LM2700 is that it operates at a higher frequency (600 KHz), uses a smaller inductor (22 uH) and is more efficient (90%) than the LM2577.
I can't link you to the order page, because you will have to establish an account to get there.
John