The one I saw was on Viator which has some other options. Unlike other countries where I have traveled I've found it easy to join a group as a solo traveler or just a smaller group that didn't need or want the private tour routine. Seems in this region most packages are based on the number of people booking. Which means pricing of ~130USD-195USD.
Have you reached out to your hotel to see if they can arrange you joining an established tour at a reasonable rate?