The NRA maintains a list of all sanctioned matches. It can be found as a link from the website for Shooting Sports USA.
http://www.nrapublications.org/ssusa/
The link is on the right hand side of the page. The list is for all shooting disciplines, so you will have to find highpower on it.
There are matches held at University Rifle Club in Reading, here is the match program.
http://www.pennarifleandpistol.org/c...iversityhp.pdf