Most guys go to a aftermarket system from cranesmart, or lsi, or hirschman. Hold onto your wallet, depending on the options you want- could easily spend $4-7,000, depending how much info you want displayed. A2b, Scale, boom length, boom angle, wind speed, etc.
On my older cranes, I generally mark boom length with stickers on the boom, install a manual / mechanical boom angle gauge, and buy a cranesmart radio scale. If you have a scale, boom angle and length, you should have all the info you need, to safely operate. Just the scale with display is usually $3,500- $4,000. Any additional sensors you want (A2B, boom angle) add at least $1,500 per sensor. Boom length is really expensive because the reels are really expensive. Last I priced it if you wanted all the info and it to work as a function cut out- you end up on the far side of $10,000.
The old krugers are pretty tough units, do you have any idea what is actually wrong with yours? I know that if you could find a good electrical repair man- it will be far cheaper to fix yours as put in new.
As far as I know- no parts are available for the old kruger's. Parts are becoming really hard to find for the Greer systems that were used after it. That's the reason everyone goes aftermarket- there are no parts available