Bisleyjohn,
I was hoping you would intercede. Peter Dyson looks like my first lead. To say I’m ****** about this is an understatemen.
First I want to say Do Not Be Discouraged
This part can be made from scratch and your lock will work as good as new again.
The only part I see missing in your picture is a pin that links the fly to the spring. Thanks to your good photos it looks like crystallization of the metal caused the failure. In time it would probably fall apart.
To find tiny parts, get down on the floor with a strong flashlight that has a focused beam. preferably one of the new ones that has an LED type bulb. Shine the flashlight against the floor so the beam makes a track across the floor like a lighthouse shows on the water. Any little thing on the floor will reflect the light and you will see it. If you have cuffs if your pants check those. Little parts bounce and land in amazing places. You can try a vacuum cleaner, start with it cleaned, rinse and dry the hose and nozzle. New bag or wash and dry the bin. Vacuum everything everywhere, then search the vacuum.
Save the broken parts and keep them in a marked container that is guarded at all times.
Do not send these parts to anyone until you have precise measurements, photos, and a really good plan.
I am using names that may not be correct for naming the lock parts. But the names make sense to me. Feel free to identify the parts I am discussing.
In the picture the spring is removed, the rocker cover is removed and shown. The fly as you can see is mounted to the arm of the rocker with a small pin. The end of the spring has two hooks that engage the fly. On this lock the T shaped part engages the hooks at the end of the spring.
If you look at the picture with the broken fly, the spring has two hooks. The broken fly has two hooks. These two pieces are made to sit side by side in the location with a pin allowing the hooks to have rotation at the intersection.
What I see needs to be done since there is a void of technical information needed:
Mate the broken pieces as if not broken - and please no glue, welding or holding with fingers!
Measure the part and record using a Computer Aided Drawing (CAD) program. When this work is complete, an exact representation of the broken parts will be drawn as a completed part. Use a quality digital readout caliper and a micrometer with readouts to 00.0000 and make all measurements precise. use a measuring pin set to measure hole sizes.
Once you have a drawing, the part can be made.
Select the metal.
Decide on heat treatment.
Machine the part to tolerance.
Fit test not under load or stress.
Make a spare one or two
Complete heat treatment
Fit test
Test under load
Verify part is operational
My worst fear in all this is you lose control of the broken part. Finding one person to do all this is a quest. Finding a specialist in each of the categories is much easier. BE VERY CAREFUL
Again, do not let the parts out of your direct control until you have an exact drawing. Even if it means standing there watching them work.
When it comes to shipping valuable items, box it big enough so it cant' be "lost". Insure for the maximum amount. Require next day signed delivery. Use Fed Ex or UPS or similar carrier but do not ever send via some government outfit. Don't ever use a Fragile label. Packaging should stand up to being crushed and blown up.