Weight inside handlebar fell out, end weight now rotates freely

Bike was knocked over by wind months ago. The left handle bar end weight became loose from the impact and I lost it while riding.

I've also noticed that one of the outermost weight inside the handlebar itself fell out. Any new end weight I put on the left side is free to rotate as there no locking mechanism to keep it from getting loose.

Is there anywhere I can get replacement weight for inside the handlebar?

The bits are listed on Lings, you may decide it's cheaper to do away with the stock bar end & weight on the other side and replace it with after market! I bit the bullet because I wanted to keep it stock.

Thanks for that. Just looking at the diagram, it appears that no.7 weight on the diagram was fractured and the broken piece came loose and fell out of the handle bar. 

What's the best way to get that broken weight out? Would threading a screw into it and pulling it out work?

Same thing has happened to mine and I've been riding around with one bar weight for weeks.
There is a metal ring clip thing in the end of the bar that needs to come out first - you can pry it out gently with two flat screwdrivers on the tabs.
The bolt from the weight you still have is probably the best thing to pull it out with. If it broke like mine (probably did) then there'll be enough thread in there to get a grip on and you can haul it out with a pliers. It's lodged in there with some rubber grommets and rust but it'll come out!

I wonder has anyone replaced with aftermarket ones and noticed any difference in vibration or anything?

I might either be in the market for a spare internal weight or selling a pair of end weights + one internal.

If you can fit some threaded bar or long bolt into the weight throw a large washer over it to butt against the handlebar & tighten a nut to draw the weight out.

My current steed came with aftermarket bar ends & it's a touch more vibey than the last one that had standard ones. While it doesn't bother me much I do consider getting these 300gram weights (most aftermarket ones are under 100 grams each) from time to time to smooth things out.

That metal ring clip is missing as well. Will I need a new one?

The ring clip is what holds the weight into the bars so you'll need it if fitting bolt-in weights .  The aftermarket ones with an expandable section don't use them.