Ok I am going to post websites for the UVB --- but please move the digital probe thermometer to the basking spot where he sits - you want a surface basking temp of 150-110 for now --- hes a baby still at 4-5 months --- at around 6 months that temp is going to change to around 95-110- he should be pooping every day right now -- as they get older the pooping will slow down but for now it should be at least once per day so I am thinking those surface basking temps are not hot enough to start the digestion going - now for the UVB we need to replace it w/ one of these
for a tank of 40 + gallon a 24" fixture like a Zoo Med 24" this will come w/ a 5.0 bulb good for small tank of 40 or less but you will need a 22" Reptisun 10.0 T 5 bulb for a tank of 40 gallon - keep the 5.0 bulb it can be used as a back up but placement and distance is different from the 10.0 bulb
Zoo Med ReptiSun T5 HO Hood Zoo Med ReptiSun 10.0 UVB T5 HO or this it can be found at Pet Smart if you have one or order on line they are a good fixture and bulb 24 watt
Arcadia Reptile ProT5 UV-B Kit | reptile Light Fixtures | PetSmart
or this fixture you will need to change the bulb out to the one posted above Reptisun 2 ft or 24"
https://hydrobuilder.com/sunblaster-nanotech-t5-ho-fixture-with-6400k-lamp.html
placement and distance will be determined by the screen on the tank - please post when you get the UVB so I can help you get it placed for your tank -