I'd be careful with the stanley site -- the blades for their last-gasp plow planes, plastic-handled versions of the #50, may not actually work in the 45.
My #50 is pre-adjuster. The #45 blades are too long to work in my #50. The #50 blades might work in a #45, but they have a different adjuster.
The 'bay lists cutter sets all the time, so that may be your best bet, even if it means picking up another 45 along with the cutters!
Sometimes it is handy to have a full set of blades and a second body with the #45. This allow for different set ups for a job without having to change back and forth.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)