Unfortunately, there are no disease modifying drugs (DMDs) available for SPMS at the present time (this may change, and as Carole said, there could be trials that you could be included on. The only treatments available right now are physiotherapy, drugs to help with symptoms and things like orthotics to help with various problems (as you know, having an AFO). And obviously alternative treatments, including dietary changes, vitamin and mineral supplements, Hyperbaric Oxygen Therapy (if there is an MS centre with an HBO tank near you, it might help) and mindfulness meditation, which many people swear by.
Simvastatin has been shown to help reduce brain shrinkage in later life. If you have any cognitive problems now, it might be worth giving it a go. I actually found it made my legs a bit weaker than usual (checked the side effects and that is a known possibility). But we are all different, others have found it helps.
Physiotherapy and/or exercise is always good, it might help you maintain your current state of health for as long as possible.
Since I’d had bad side effects from several DMDs, I wasn’t on any. So when I was described as having moved into a progressive stage of the disease, I was actually quite pleased. At least, I thought, I won’t be having any more potentially disabling relapses. Then I had a proper relapse a couple of months ago, with both sensory and motor symptoms (having to be helped onto the loo, into bed, etc, was just a bit worse than normal for me). Luckily oral steroids sorted out the relapse, they actually did the best job ever. Only IV steroids had done a better job in the past.
So this means I am now re-labelled (again) as Progressive Relapsing. The worst of all worlds. But, I may be able to access DMDs. If we can identify one that I can take, and the neurologist thinks I fit the criteria.
So, the point of all this is that if you are still having relapses, try to resist the label Progressive. if you are definitely not relapsing, then there really are no DMDs. So all you can do is treat symptoms and try to get your muscles as fit as possible. And hope that any progression from here on is slow and gentle.
Best of luck.