You'll have a better chance simply hiring a rogue/dark caste clansman.
1. It's one thing becoming a bondsman to the one that defeated you; you don't just go to anyone that wants you...
2. You don't just pick up a bondsman in a POW camp, like an abandoned puppy.
3. You could theoretically "buy off"/ransom/bail a clansman from a DC POW camp; it probably won't be legal, but can be done probably. But he won't be your bondsman, and have no obligation towards you since you didn't defeat him.
4. In clan culture mercs are scum. Security guards (AKA rent-a-cops), are second line scum. They're so far down the line of respect, you can't even find it with a map.
But not all is lost, just forget the "cheap labor bondsman" concept. Clansman are the best at what they do, and they know it; treat them accordingly. Offering him to train a unit that he will command, is actually a pretty good deal. Try downplaying the "security" aspect, and use fancy words like "elite crisis team" to emphasize all the ass he'll get to kick, theoretically. Being a Clansman POW, is to be non-person in clan culture, and the dracs are probably aint doing him any favours (might actually want to go to Davion and Steiner camps, since they're less likely to abuse their POWs, Dracs probably execute them on whims). Emphasize the "you can get back in the fight under my sponsorship, or you can stay and rot in this hell-hole", and that you'll give him independence in how he'll train and lead the unit. In the end it depends on the guy, some of them simply resign themselves to slow and dishonorable death, while other might be more adaptive and say to themselves "well that part of my life is over forever. What's next?".