I recently considered adding an extra trigger / pad to a Roland e-drum in order to use for triggering a cowbell or similar things.
I found the following options:
Roland BT-1 bar trigger
Price: from 110 USD
Attachment: attaches both to snare or tom screws as well as any standard L-rod.
Triggering: mono (connected to stereo in order to improve crosstalk)
https://www.roland.com/global/products/bt-1
BT-2A (noname) bar trigger
“Compatible with” ( = clone of) Roland BT-1
Price: about 35 USD, e.g. on AliExpress https://www.aliexpress.us/w/wholesale-edrum-bar-trigger.html
Attaches only to snare or tom screws. The attachment is also a bit flimsy according to reviews.
Triggering: mono (connected to stereo in order to improve crosstalk)
GRV VB-1 also known as HXM NL-1 (noname) bar trigger
HXM NL-1 and GRV VB-1 are different names for another clone of Roland BT-1.
Price: about 70 EUR
Triggering: mono (connected to stereo in order to improve crosstalk)
Reviews are pretty solid, the only issue is that it attaches only to snare and tom screws. It’s missing the additional attachment part of the Roland BT-1, even though it would be compatible with it.
Jobeky Electronic Cowbell
Looks like a real cowbell.
Price: about 40 GBP (plus worldwide shipping, to Germany it is 12 GBP)
Mount type is not specified. According to one review, it comes with its own holder. It also mounts to an L-rod, however Roland L-rods are too large in diameter.
Triggering: not specified, probably mono
https://jobekydrums.co.uk/product/jobeky-electronic-cowbell-2/
Jobeky Electronic Jamblock
A red, “digital cowbell” looking thing.
Price: about 40 GBP (plus worldwide shipping, to Germany it is 12 GBP)
Mount type is not specified, judging from the image it mounts to a cymbal holder/rod?
Triggering: not specified, probably mono
https://jobekydrums.co.uk/product/jobeky-electronic-jamblock/
Electronic Cowbell With Built-In Trigger And Holder
Not available anymore?
https://worldrummers.com/product/electronic-cowbell-with-built-in-trigger-and-holder
Triggering: mono
Terrible reviews on youtube, critizing build quality as well as the super flimsy and bad attachment to the drum kit.
E.g. https://www.youtube.com/watch?v=gdOThEjh-OY
DDrum Tube Trigger (Europe)
Not available anymore.
Price: about 30-50 EUR (used)
Attached using standard L-rod.
Triggering: mono
Uses XLS connection, so a special cable is required.
Some information:
Pintech Tube Drum Trigger Pads (US)
Similar to the DDrum Tube Trigger above. Comes in 2 sizes, 6″ and 12″ length
Price: 55-75 USD (plus worldwide shipping, to Germany it is from 33 USD)
Mounts with its own included multi clamp.
Triggering: not specified, probably mono
https://www.pintech.com/product/tube-trigger/
Pintech eWedge Trigger Pad
Wedge shaped trigger, looks similar to a cowbell.
Price: 90 USD (plus worldwide shipping, to Germany it is from 50 USD)
Attaches to stand L-rod.
Triggering: not specified, probably mono
https://www.pintech.com/product/ewedge/
Build Your Own DIY Cowbell
The following reportedly works well:
Buy a cheap acoustic cowbell, drill a hole. Add a piezo trigger and trigger socket. Add some rubber (rim silencer) to the front edge and some rubber mat on top and fill the inside with something sound insulating.
You know more options?
Please add them to the comments!