The only 45mm I've managed to acquire is a Chinon Auto 45/2.8 in KM mount. Neat! Sharp! And just US$14 shipped.
Next closest is a Meyer Helioplan 40/4.5 in Exakta mount (US$13), easily adapted to PK -- glue a M39-M42 ring around the Exakta bayonet, grind ~0.6mm from the flange of a cheap Bower-type M42-PK adapter (I used 100-grit sandpaper), screw together and shoot.
A dedicated lens-hacker might pull the Yashinon 45/1.7 lens from a Yashica Electro 35 GSN and mount it on an M42 helicoid or a trashed lens body. But I don't want to kill my Yashica. Maybe if I get some junker rangefinder...
This
MINOLTA MD ROKKOR-X 45MM 1:2 is currently at US$1 with 0 bids and US$7 shipping. This *might* be adaptable to PK by removing its base aand replacing it with a wide-flanged M42-PK adapter, or the body might need a little grinding to reach infinity focus.
A bit kinkier: this
Isco Optic PC-ULTRA-AV 45/2.8 projector lens might be adaptable by sticking it into a cheap PK macro tube set. I've done similar with a Schneider 60mm PC projector lens. No iris, so shoot wide-open, or cut Waterhouse stops from construction paper.
The Pentax FA43 Ltd is in the US$600+ range. Ouch. And it's overkill for a K1000.