What you need might not be physically possible: it depends on what you mean by "not massive". All the UPS'es I've seen that can supply power to AC drives are the sort that need a rack of batteries.
You definitely want to pursue a UPS that supplies bus voltage to the AC drive; just keeping the control board active isn't enough. Precharge cycles not only take time but also wear out the precharge rectifiers..... I wouldn't expect a drive to last more than a week under that service, maybe less.
Could you consider using another AC drive as a DC charge reservoir, with the buses connected together ? A typical small drive will hold up the DC bus after the main power is removed for 10 seconds... a big drive (say, 50 HP) will keep it up for several minutes. If you could use a high voltage UPS to keep the drive "topped up" and prevent the precharge from engaging, it might work.
Start by putting some numbers down: how many watts will the control system need, how many will the drive need, what kind of enclosure footprint do you have, and how many kilograms is "not too massive" ?