I would recommend *** that you use a fingerling yarn weight or sport weight yarn (or even better,one of those crochet yarn thread cakes in #300, which is so thin that it is almost thread thread)...
Then I would suggest that you measure your bearded..and use the measurements to make your own whatever..
Example: measure from:
1) Neck between shoulders back down to its back legs: A
2) Circumference/Around at its widest point/add a quarter or half inch as it will need space for movability and comfort: B
3) Circumference/Around the widest point of its head/would need to slip passed/over this point: C
And use those measurements to design a simple garment. Casting on however wide or long a garment you need to make based on those measurements, and then just use a simple Knit and Purl repeat to keep it simple...until you've made your 1st basic to get the feel of it. After you finish the 1st garment then you'll be ready to tackle a 2nd fancier (& will know if it will fit or if your measurements or even what & where you measure are accurate or require adjusting.)
*** That you be very careful, as your dragon could certainly snag its claws on whatever you create, and definitely would snag itself on whatever else is in its habitat..and do NOT EVER leave it wearing whatever unattended, as it could injure itself, get hung up, possibly get choked, etc.
Good Luck!!
UPDATE: Corrected typos...&..Never had a bearded, but did have a Savanah Monitor
