The original poster asked if there are other brands of antennas of the mag mount type other than the 'top three'.
Yes; there are. But did you ever ask your self what they aren't in that 'top three'?
Prolly because that didn't make 'the grade'.
A mag mount is a compromise of a solid mount antenna. But I've always been pleased with the mag mount antennas I use. So long as it is mounted on the top and in the middle they usually work very well.
A Sirio and Wilson are fine and I own and use them both - alternately.
Gave away the last K40 I had. Never tried a Lil Wil; but I did help a friend get his working. I think they work at the same level as a K40. The K40 is just OK; but the Sirio and the Wilson 1000 or 5000 are the real talents here - IMO.
As to your limit of $50 for an antenna, I would get a used Wilson 1000 or 5000. Because at that cash limit, you aren't going to get a fine antenna for new anyway . . .
Who sells Sirio antennas in this country?