I have a Pool Star underwater light for my guinite pool.  It takes a 12v 300 w max bulb lamp R40.  The model number on the cannister is PLH-300 with these numbers also - H-744572.  It also says use with housing model No's 425 and VN50.  The lens appears to me to be 8 " across. I also understand that Pentair bought Pool Star out.  Any help in finding the correct gasket that seals the lens would be appreciated. 

Also, if I have to replace the whole unit, can anyone advise what would a similar unit would cost,  and also the approximate electrician installation costs. 

Thanks - I appreciate any help!