What is the HIV transmission risk if a dancer on top of me rubbed her moist vagina on my penis, with 2 layers of clothing in between. I ejaculated. TY?

HIV transmission. HIV transmission highly unlikely in your case.
Zero. She is no more going to give you HIV than you're going to get her pregnant doing this. Little, little brother. You're a man now. You got a lap dance. There's no exchange of fluid, and exactly no risk to you -- even of getting crab lice. Put away these childish fears. Sexuality is frightening, and this might be a great time to talk with some sensible grown men -- maybe even Dad.
You are safe. Firstly, dancer on top would have 2B HIV +ve. Secondly, her "moistness" would not only have to pass thru your 2 layers of clothing & into a cut or abrasion on your penis.
Here are some... Your described scenario should pose a zero odd to contract HIV since there is no fresh break-down of natural barrier - skin or mucosa; hence, there is no access to transmit HIV. This is what I know according to my 45-yr of study and practice in medicine and urology. In fact, there is no known study ever designed and conducted to specifically address the concern you raised.