I have a cylinder from each of these places and like both of them. Good construction, excellent seal:
PictureBrite
Picture Brite Retail P125 - Jim Diamond 2 1/4 inch cylinder w/free metal pump $27.95
Description does not say but it is 9" long. They may sell it with out the pump, I didn’t look too hard. (I got mine from them on ebay, which was slightly cheaper.)
Boston Pump
STANDARD DESIGNED CYLINDER 9" length - $55.50
With the Boston one, if you want it longer, it is $5.00 extra per inch.
Both cylinders work great. Note that the Boston Cylinder has what they call a "built in cockring" — basically that means that the entrance is a little narrower and thicker. That makes getting a seal a real snap.
In my experience, Boston Pump was slow to respond to emails and slow to ship. However I did receive my gear and it is excellent.
With picturebrite, shipping was fast, but there was a mixup in my order (wrong cylinder). When I contacted them they immediately shipped out a replacement, which I had in a day.
So in my experience both companies were great and the products are great.
Hope this helps.