positive battery terminal connection screw not securely fastened.

[Toner]

I was topping up electrolyte levels in my battery today with distilled water. I took the battery out to see the levels as I couldn't make them out in the bike.
When re-inserting the battery, I noticed the positive terminal connection screw did not screw down tightly into anything. It's pretty much just resting there in the hole.

I didn't notice this when taking it out though I probably should have.

Anyone know what I can do to fix this? Is it important? I haven't had any trouble with the bike's electrics since I got it a year ago second hand.
It's a 2000 model.
Bigger screw perhaps?
Should it screw into a nut below?

Also I should have paid more attention to where that drain tube that hangs off the battery goes. I kept it tight inside the battery container shelf and then it drops down through a space in the floor and hangs down near the suspension spring. That ok?

[gsJack]

Screws into a square shaped nut below and they fall out and get lost easily.  Battery vent hose goes across behind the battery and and down and comes out with a couple other hoses near your right foot. 

[Toner]

Oh yeah I see that square nut on the other terminal. How is that secured in there? Looks like it's welded in. Maybe the corrosion is holding it in place.

Don't know how I lost that square nut but the garage goblins have it now.

Is it very important? And is it something I can buy? or would I have to get a whole new battery? Perhaps I'll try and use a regular hex nut but I don't know how I could hold it in place while I'm screwing the screw in.

[Suzuki Stevo]

If you havent lost the square nut you can cut 1/2 piece of drinking straw and put it under the nut, heated gear harnesses and battery tender hookups sometimes make the screw a bit short to reach the nut.

[Toner]

managed to get a bog standard m6 nut in with a bit of fiddling. Hope I remember about it when it comes to unattaching the lead again.