There are at least two other similar continuous ringing mountain bike trail bells:

• One sold by Art's Cyclery -- it's a miniature cowbell and costs only $5. It doesn't seem to have a disconnector to stop it from jingling. Pretty much like my homebrewed jingle bells. When I wanted to quiet them I'd just remove it from the handlebar via a quick release and put it in my jersey pocket or saddle bag.
• The other is the "Awareness Bell" -- it's pricey, costing $40 -- more with customizing -- but they're handcrafted by one guy and have a beautiful tone, probably the nicest of these three mountain bike bells. The disconnector isn't quite as handy as the Timber bell. You can find a couple of demo videos on YouTube.

Keep in mind these trail awareness bells are only as good as the terrain. They don't ring much on smooth pavement. But I found my homebrewed jingle bells really handy and friendly sounding on the local MUP, where the paved path is basically just a sidewalk -- the seams every few feet were enough to jingle the bells, and the jingling was more noticeable on gravel. But on most paved streets it barely jingled at all -- some folks in group rides thought it was just something coming loose on my bike, not a bell!

The nicest sounding and most distinctive bell I've heard in local group rides is the Sunlite type ding-dong bell. It has two successive tones with each stroke of the clapper. Besides being louder and more resonant than most smaller bells the two tones also seem to help give a better sense of orientation -- position, direction and speed of the bike using that ding dong bell. And they're among the least expensive bells around, although I don't know how well they hold up. The fellow I know of from local group rides who uses one on his cruiser says it's held up well for him.