ETrailer is a good source and has good service.
I would NOT recommend a Bulldog Jack. In our case we use a weight distribution system where you lift the trailer up high then put on the WD arms. The Bulldog Jack has a slight glitch in its design that when fully extended you can strip out the gearing and it won't lower the jack. We then tried to manually lower it and twisted off the lug.
I only found this out after googling and You Tubing Bulldog Jacks as I was trying to problem solve. Bulldog and ETrailer acknowledged the problem and honored a return.
Bulldog appears to make a good product and when it worked it worked well. Just not with our lifting to its limit.