My bicycle has a front derailleur. It's a hybrid. I use it to commute and would like to fit a chainguard.
Is there any chainguard that can be fitted when there is a front derailleur?
There are a few plastic chainguards for front derailleurs.
I never found a full chaincase but managed to fit this de Woerd Wave chainguard to a mountainbike used for commuting (3×7 gears I think). I failed to get the same model working on my 3×8 hybrid, though it had the same chainrings as the MTB. I would go on, but I couldn't avoid it rubbing in some gears because I couldn't get the bottom bracket clamp to sit straight, and never got round to modifying it enough to make it work to my satisfaction.
Holland bike shop has a wider range of de Woerd parts; some are specified for double or triple chainrings. I'm sure there are other makes, but these are the ones I've come across
A double chainring would be easier to work with than a triple, but you may have to modify the chainguard a little - easy if it's the fairly soft plastic part, but harder if it's the mounting brackets (which have to be secure to be safe).
With all the expertise here on SE, I must be missing something, but I throw this out there: Usually I don't have chainguards on my cranks and have no problems if I've strapped the right cuff of my pants. For about 9 months, I ran the pictured crankset, was able to leave the strap off my leg and had zero problems. For whatever reason, sweatpants--the nylon shell type ones--are the biggest catchers of the chainwheel unless secured. Even these remained immune to snags with this device. It was nice to be able to hop on the bike without regard for what I was wearing or the need to find a suitable strap to secure my pants leg.
These chainwheels with chainguards are available on low to medium-end models, but I believe the touring version of an XT crankset (FC-T780 or T7000) has an optional chainguard. At any rate, this ring of plastic did the trick every time irregardless of what I wore.
The two general purposes for a chain guard are:
If you're only looking to keep your pants out of the chain, this DIY project would work for two chainrings: Chain Guard Made From Chainring
The above option might also fit on a triple crankset by using longer chainring mounting bolts and spacers. The challenge is having sufficient room between the chainguard and the crank arm. A gap cut in the chainring could be used to provide clearance for the crank arm. Aluminum chainrings are soft and easy to work with. Steel, not so much...
If you don't want to fashion the above DIY chain guard you can also search the internet for "bicycle bash guard" and also "bicycle chain guard". You should see many options, but it may be a challenge to get one to fit. FWIW, the ones I saw were $45 to $65.
A couple more thoughts:
If there is a bike co-op or similar non-profit in your area. I volunteer at one and we get lots and lots of donated bikes to recycle so there is never a shortage of stuff to rummage through and you might find something which will fit. Similarly a local used bike shop may have something.
Changing the bike to a 1x setup will give more options as this makes for a simpler setup. Or if money is no option there's a really really nice (and expensive) 14 speed internal gear hub (IGH) which would make fitting a guard much simpler. :-)
Good luck, Greg