My 6.9 has always had a weak right front strut although it never particularly leaked externally.
The struts are no longer procurable new but I purchased two kits of seals off US E-bay last year.
I also understand Styria sells reconditioned exchange struts and this was my next alternative - and looking back on my experience probably a sensible economical one as well.
I appreciate this is his business and have no desire to tread on his toes but here is a record of what I have been up to...