Mine was broken in exctly the same way and because it wasn't my first QP I was in the habit of lifting before pulling back for reverse. So I didn't notice for some time that it could click the reverse microswitch by just pulling back without lifting. I was looking for broken or wobbly, and it was fine apart from not needing to lift.
Anyway, I fixed mine for under 3 quid, and it's not much work:
Buy a 50mm piece of 2.4mm dia titanium rod for £1.79 delivered:
http://www.ebay.co.uk/itm/111712980353
Drill out 2.4mm holes exactly where the broken bits attached. Use a 2mm drill and widen until the rod just fits.
Then use a vice & hacksaw to cut the rod to fit the hole and protrude the right length.
Use JB Weld epoxy metal glue to glue in the pins you've made. After wiping off surplus glue, Sellotape the brass bushes over the pins to hold them in the right position while they set. I already had some JB Weld, and you only need a minuscule amount, but it's an extra £5 or so if you don't.
After 4 hours tidy up the glue whilst set but softish.
Leave somewhere warm to harden for 24 hours.
I had to buy a new bolt as the original one that holds the fork to the handle had been glued in by a botcher and I had to drill it out. I bought 5 for 99p:
http://www.ebay.co.uk/itm/121543512907
You need M3 0.5mm pitch thread, 20mm long for the QP. I used a bench grinder to reduce the head diameter so that it would fit in the fork recess.
Use threadlock on this tiny bolt to prevent the handle coming loose.
Grease/reassemble.
On mine the black hard plastic handle had a small broken section, I tried a glue for hard plastic unsuccessfully, then JB Weld and it has done the job. I also tidied it up and resprayed it with plastic primer and Halfords bumper paint, and it looks almost as new/original.
Note that there's nothing to stop you fitting the QP handle facing the wrong way. The plastic bit is less likely to break if you fit it the correct way, as shown here.
With this info you could probably do it in 30 mins, if you have the tools. So worth it for a £110+ saving for most of us.
The problem with the Hill Engineering solution is that they use larger diameter pins and do away with the brass bushes. This means that a muppet forcing the lever back without lifting (how they get broken) will more likely break the fork rather than a couple of pins, possibly leaving you unable to select reverse.