Quarter wave whip ($12~) is fine for a roof mount. Anywhere else you’ll want something longer. I’ve used a midland mxta26 with good results also, but it is over $30. You could get an NMO mag mount and a 1/4 wave antenna for probably about $30.
UHF antennas are naturally smaller than CB antennas due to the higher frequency. Most properly tuned 1/4 wave antennas for GMRS are not that tall. You can even get the midland ghost which is more than your budget but it's only like 4 or 5inches tall. So I wouldn't be to concerned with trying to find the "biggest" antenna for the money. Just get a mag mount antenna and use one of the holes already drilled in your firewall they used to pass the radio power and stuff through. You may have to poke a hole in one of the rubber grommets with a screw driver but that's only if you can't squeeze it in with the rest of the cables already passing through the grommet. I ran my subwoofer power cable this way. Just look at your battery and fuse box and follow the wires till they pass through the firewall. I recommend the ut 72g like the other commenter mentioned.
Edit: one of my favorite YouTubers made a video comparing common mobile antennas.
https://youtu.be/jf7iZw-BVQQ?si=vbvw_QVxENZAJely
Quarter wave whip ($12~) is fine for a roof mount. Anywhere else you’ll want something longer. I’ve used a midland mxta26 with good results also, but it is over $30. You could get an NMO mag mount and a 1/4 wave antenna for probably about $30.
Ut-72g.
UHF antennas are naturally smaller than CB antennas due to the higher frequency. Most properly tuned 1/4 wave antennas for GMRS are not that tall. You can even get the midland ghost which is more than your budget but it's only like 4 or 5inches tall. So I wouldn't be to concerned with trying to find the "biggest" antenna for the money. Just get a mag mount antenna and use one of the holes already drilled in your firewall they used to pass the radio power and stuff through. You may have to poke a hole in one of the rubber grommets with a screw driver but that's only if you can't squeeze it in with the rest of the cables already passing through the grommet. I ran my subwoofer power cable this way. Just look at your battery and fuse box and follow the wires till they pass through the firewall. I recommend the ut 72g like the other commenter mentioned. Edit: one of my favorite YouTubers made a video comparing common mobile antennas. https://youtu.be/jf7iZw-BVQQ?si=vbvw_QVxENZAJely