I was fully vaccinated with pfizer 9 months ago and had a breakthrough infection with delta 5 months ago - is there any data to show what my chances of getting omicron are?

Too early for specifics. It appears that someone with your history might get omicron, be symptom free or have the equivalent of a head cold. As of 12/30/21 there were about 10 worldwide fatalities cited for omicron although it is dominant in many areas. It seems to target the upper bronchi, head & throat rather than the lungs. Time will tell but omicron may be a Christmas present to the world.

Despite your vaccination status and breakthrough infection it would be prudent to get a booster dose to improve your chance of escaping infection. Wish you good health!

Small. chance, but not impossible. Reduce your chance of reinfection by getting a booster.