I've never heard of selling or re-filling one that shoots "slime", maybe outside of a kid's toy version, but for anyone else curious about them:
1) Firefighting foam can be pretty bad for you - depending on composition, the extinguishers can be filled with any variety of irritants or toxic chemicals.
2) Seriously: Avoid powder/dry chemical extinguishers like the one pictured altogether; You may die if that shit gets in your lungs.
You may, however, be looking for Avalanche Foam. You can get it through Messy Supplies, it's non-toxic, and I think they have a toy gun squirt...thing... you can dispense it with. It's probably the closest to what you're looking for.
It's so much more complicated than it sounds. In stage, film and TV it's usually a task sub-contracted out to prop making/visual effects professionals as each individual application tends to bring up its own set of problems and solutions. Many of the most effective solutions involve a gutted or fake extinguisher hiding some form of mechanical propulsion device involving compressed air or Co2.
Refilling a liquid extinguisher (and its appropriate propellant) is a specialised service sold as part of a rental or purchase contract and not an easy thing to do at home unless you've got a very well equipped workshop and you're very mechanically adventurous and/or competent. Certainly not a casual task.
I spent some time a few years ago creating a compressed air device for propelling gunge and paint safely using a compressor that was never fully realised before I gave up my studio space (it was an incredibly cumbersome prop!) If I resume producing it will most certainly make an appearance!
It's a good topic, though (like gunge tank building), for discussion.
If you can find a large extinguisher that uses WATER (it NEEDS to be a water one as others are chemicals mentioned in previous comments) you can refill those with a substance of your choosing and use a bike pump to get pressure. If you look up videos for fire extinguisher graffiti that would be your best bet. That being said, you probably can't have it thick like slime would be, but they can definitely shoot paint upwards of 20' so do with that information what you think is appropriate.
You'll need an empty one that can be cleaned out. You need to depressurise it and remove the headcap. Fill it with slime or watery custard about 3/4 full.
Put the head cap back on. The recharge it you need to connect it to a compressor. A standard UK fire extinguisher is usually charged to around 8-10 bar pressure.
I've not done this with wam substances but I used to refill water ones to train fire marshall courses
MidsWAMGuy said: You'll need an empty one that can be cleaned out. You need to depressurise it and remove the headcap. Fill it with slime or watery custard about 3/4 full.
Put the head cap back on. The recharge it you need to connect it to a compressor. A standard UK fire extinguisher is usually charged to around 8-10 bar pressure.
I've not done this with wam substances but I used to refill water ones to train fire marshall courses
Would you be able to recommend any fire extinguishers on amazon (UK) that would be suitable for this? Loads come up, but I can't be entirely sure if it's refillable or not...
Is it possible to pressurise them with a foot bike pump? Does it need an attachment to be able to do this?