same situation but looking for code for 20" tv/dvd combo
(IS-TV040921) that i bought from best buy. but just found
this list of codes from insignia website:

[Link: insignia-products.com]

it lists model number, best buy part number and codes
for different universal remotes - phillips, directtv,
rca, oneforall and sony. for my model, the codes are for
the tv functions ony.

haven't tried them yet for my comcast ondemand remote
but if any work for you, please post! i'll update with
my results and keeping my fingers crossed!