You've got several options for a tag, but not all will directly fit your faction name. You could use TJ - Trafalgar junkers. Or simply -J- or something similar to signify yourselves as junkers without using JU- or .:j:.
Another option for you, being in bretonia, is to operate with the bretonian armed forces as privateers and mercenaries against kusari - either in combat or as smugglers carrying goods to bretonians on the front lines. This will create more interaction between the junkers and hogosha as well, whereas currently there is little to no conflict between the two groups.
Junkers in each of the major areas we operate in have specific enemies they have to deal with. The junkers in liberty have the corrupt and tyrannical liberty lawfuls - there's more resistance to smuggling and piracy operations in liberty than anywhere else. Out in rheinland/omega15/sigma13, the junker's union has a lot of issues with bounty hunters due to their 'war' against the harvesters, DW bounty hunters in particular. We've also got the rheinland military to deal with, though we try to keep a legal face so as not to antagonize them.