I've had good luck with Deltran, and the one Harley sells (looks like a Deltran, only has the HD logo). I've had up to four at one time, and none ever failed. I've got one I'm using now that's been on some part of nearly every day for 2 or 3 years.
In contrast, I purchased two from Harbor Freight at about 1/3 the cost of the others. Both lasted about 6 months. After the second one died, I figured it out--there was an inherent flaw in them--and went with the Battery Tender.
I wouldn't be afraid to bet Sears is selling something akin to those I got at Harbor Freight. I know I've seen the exact same drill-press at Sears as at HF, only the logos were different...