Don't know if there's anything available nowadays, back in the 70's there were quite a few kits to do this sort of thing. Basically most were a tube connected in the car heater pipework, and wrapped round the washer tubes. Also some electric types, which were electric heater elements, again wrapped round the washer pipework. Don't think they were truly effective, anyway.
Add 50/50 windscreen fluid to the bottle of water when it`s nearly empty. If it`s frozen now spray hot water over the plastic pipes to thaw them out and keep on squirting the water until bottle is nearly empty as previously said.
Conventionally, you would increase your screenwash dilution to 1:1 (or whatever the label recommends for winter conditions) in anticipation of severe cold weather.
A squirt of antifreeze on the nozzle before you commence scraping your windscreen may help free things up.
If you can see (or feel) ice crystals in the pipework (screewash too dilute, say), then you'll just have to wait for the warmth of the engine to thaw it out. The shorter your commute, the less chance there is of this happening.
There's not much you can do if the weather is really cold and the washer hoses have frozen Stardetta. Screenwashes do have some antifreeze properties but they are limited with the small volumes of water in the hoses and nozzles which freeze easily when cold. The hoses and nozzles may melt if they engine bay gets nice and warm but once they are frozen they generally stay that way.
The general advice on an icy morning is not to attempt to use your washers at all. If they are frozen and you try to use them you run the risk of burning out the washer motor if that is frozen too. Also check the wipers are not frozen to the glass before you start the engine as you can burn out the wiper motor if they are.
Scrape the windscreen free of ice then clean it with a cloth before your journey. Take the cloth with you in case you have to stop and wipe the screen clean along the route. Under no account should you attempt to use the washers or wipers if you think they might be frozen. It's one of the penalties of living in our climate. Just leave the switches alone. Most drivers learn that lesson after having to fork out for new motors.
Thanks for the tips everone. I witnessed drivers stopping by the roadside scooping up handfuls of snow to clean windscreens during the recent cold snap.So it occured to me that even though the cars warmed up and the wipers free to run, visability is nil unless theres clean liquid to squirt en the screen. Come on car manufacturers there's a safety issue here !
This very problem happened to me just before Xmas last year when it was very cold (minus 10).
My windscreen washers froze after about 15 minutes on the road and did not thaw for the rest of the journey ( about 90 minutes).
I had to pull over and throw snow on the windscreen to clear off the dirt so I could see.
Very scary at the time.
I have used tepid (lukewarm) water for de-icing my windscreen for decades, It is quick and efficient and avoids the risk of scratching your windscreen. If you run your wipers immediately after the tepid water has melted the ice you end up with a warm dry windscreen and don't get any more ice on the outside or misting on the inside. It also thaws the washer nozzles.