May I ask where I can obtain strings suitable for a 5 string Steinberger spirit..

[Dandelion]

I can't find anywhere online..  

 

Do I need to buy the adapter? So I can use any strings?

[hubrad]

You'll be looking for 'double ball end' for headless bass. Here's a useful start: https://www.basscentre.com/elites-dbe-series/elites-double-ball-end-v.html

[Sean]

https://www.status-graphite.com/status/frames/index_home.html

 

Status. You can phone and speak to real people.

[NickD]

Another shout for the Status Hotwires, but when I'm feeling a bit posh, Newtone strings also do double ball end.

[Bagman]

I use the LaBella flat found double ball end set on my L2 Steinberger 

 

absolutely superb 

 

LaBella make a 5 string set as well