These are made by Flo-Scan and the P/N is 201B. It is rebadged by various outlets e.g. Shadin, JPI, EI, and a variety of homebuilt avionics vendors. Ideally the K-factor should be 29800 pulses per USG.
Seems that spruce has what you are looking for:
https://www.aircraftspruce.com/catalog/inpages/mglfuelflowsensor.php?clickkey=3694
Yes; you are right. The 201B-6 is the one which Shadin sell.
What may be a challenge is getting Spruce to check their stock for which K-factors they have. Or their sensors may be totally uncalibrated. Shadin flow-test theirs and stamp the K factor on the outside.
These sensors are sold by MGL avionics for their EMS. Googling “mgl avionics k-factor” gave the answer to your concern.
So seems that Flowscan themselves specifies the K-factor of every individual sensor.
Brilliant 
I wonder who sells these, preferably stock, in Europe? There seems to be a number of sources in the USA, which is OK.
The main issue is that I need to buy it from someone who can visually see their stock and pick a suitable k-factor. With a distributor, you can’t tell and a couple have already told me they are not interested in looking at the parts.
The instrument I have doesn’t have a continuously adjustable k-factor. One has to choose values from a table:
Just to keep you confused, the IM for my actual instrument has the following table which is same as above but omits the final column!
This was partly responsible for a multi-year run-around.
Copy from http://www.mglavionics.co.za/
MGL Avionics main area representatives:
North America: www.MGLAvionics.com
Europe: www.stratomaster.eu
United Kingdom: www.parts4aircraft.co.uk
Germany: http://www.aeroparts.de
Australia: www.lightflying.com.au
New Zealand: www.sparxfly.co.nz
Poland: www.stratomaster.pl
Russia: www.veter50.ru/prib
Finland: www.windcraft.fi
Brazil: www.aerodigital.com.br
Another company that is producing a fuel flow system using the flowscan sensor.:
http://www.tl-elektronic.com/index.php?page=lsa&p_id=2
They also sell the flowscan separately.
I bought mine for TB20 at Troyes Aviation.
Dont you adjust your FF K factor to the transducer on your instrument like the JPI?
I don’t remember this feature. I just remember that I had to buy the transducer with same K factor as the one I was replacing.
Just an update. I am sorted now. Shadin did eventually come alive after I sent them 4 emails, and I have ordered two from them. They have stock with a K of 29600 which is same as the existing one. Spruce (USA or the German disti Sandelving) were not interested at all in discussing what stock they had.
One MGL disti did also reply however and they have these in stock too, with similar K factors (and, one assumes, no paperwork and about 1/2 the price as these are for the homebuilt market):
Rainbow Aircraft, Inc. dba
MGL Avionics (US)
3401 Airport Drive
Torrance, CA 90505
+1-310-534-2509
Dont you adjust your FF K factor to the transducer on your instrument like the JPI?
Yes – on some models it is done with switches (see post #5) and on others it is done from the front panel and is then usually a continuously variable value which is better.
