Intercon, Huntington, Dissolvo, Aquasol, are few names that come to mind... Here are some links:

These are water soluble:

http://www.users.qwest.net/~apcompany1005/?gclid=CMjUkofFp5MCFQQcHgod1W-d5A
http://www.dissolvo.com/welding_instructions.php
http://www.dissolvo.com/pdf/pamphlet.pdf
http://www.aquasolcorporation.com/Home/NewsandEvents/AquasolWaterSolublePaperandTape
http://www.aquasolwelding.com/techtalk/
http://www.aquasolwelding.com/products/

Here are some articles on purging:

http://www.airproducts.com/NR/rdonlyres/6AC2C3E9-40E1-4E21-8BBC-57CA2F3E27CE/0/stainless_pipe.pdf
http://www.haynesintl.com/pdf/h2065.pdf
http://www.thefabricator.com/Consumables/Consumables_Article.cfm?ID=1401
http://www.thefabricator.com/TubePipeFabrication/TubePipeFabrication_Products.cfm?ProductsID=263
http://files.aws.org/wj/2006/12/wj200612/wj1206-38.pdf
http://www.sperkoengineering.com/html/Purge.pdf

Here's orbimatic's purging accessories:
http://www.orbimatic.com/orbital-welding-accessories/orbital-welding-accessories.html

These guys are good:

http://huntingdonfusion.com/HFT/
http://www.gowelding.com/met/purging.pdf
http://esvc000163.wic028u.server-web.com/catalogue/SPW%20Section%201%20Purging.pdf

Another good source:

http://www.intercononline.com/welding/welding.htm
http://www.intercononline.com/welding/paperman.htm

Here are some more companies offering purging dams and some ideas one could use to build their own but then again, liability issues might bear fruit choosing that route especially in critical applications so, a word of caution may or may not be appropriate here:

http://www.rubcons.com/saf/products_safety_purgedams.php3
http://www.orbitalwelding.com/Pages/07-Purge.htm
http://www.pipelinesupply.com/moreinfo.cfm?Product_ID=453105929&CFID=6444772&CFTOKEN=277

Here's an interesting article from the NRC:

http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1993/in93063.html

Another on that's interesting to say the least:
http://www.cns-snc.ca/branches/Bruce/challenges.pdf

Here's an article emphasizing the seriousness of the necessary safety factors required in order to avoid accidents such as these types:

http://www.hss.state.ak.us/dph/ipems/occupation_injury/reports/docs/94ak012.htm

Very cool oxygen measuring/monitoring equipment used when purging:

http://www.tendringpacific.com/pdfs/products/SGI-3,%20OXI-3,%20ISM-3%20Oxygen%20Indictors.pdf

AMI, Mathey Dearman, Orbitalum (Formerly George Fischer), Magnatech, Orbitmatic, Cobra systems of of California, Astro Polysuede or something like it, Swagelock, etc...

Do a google search and you will find what you want. I'm going to hit the rack!!!

Respectfully,
Henry