i have rebuilt a few pressure washers, and built a pressure washer modeled after one that failed.
general pumps and leeson motors
http://www.dultmeier.com/products/search/4138 - pump for $255.
IPYVB135KDM - unloader for above pump - $53.60
i dont remember which motor i bought, but it fit the pump perfect - $ 284.55
one safety valve to prevent motor from overheating - $10
i reused the hose and wand from the old washer
all for about $603.15 plus shipping.
this replaced a pressure washer that died, it worked for about 7 or 8 years before the motor wouldnt start - a plastic cooling fan shattered inside the motor and prevented the motor from turning. the pump had been rebuilt a few times and so i bought a new setup and bolted it to the old frame. copied what the last person made and saved about $600 (looking at the sales receipt from 8 years ago).
my favorite are belt driven electric pressure washers - slower speed will make the pumps last longer.
dultmeier was friendly on the phone and had all the parts that i needed. the last company that i bought from was disorganized and couldnt get me pricing over the phone without having to call me back hours later.
needless to say, we always use ear protection - earmuffs or earplugs, also required are gloves, apron and face shield. no need to sacrifice ones health over washing screens.
if you filter the water before the pressure washer it will make your pump last longer too...