Rocker bearing collapsed

I was flat out in 5th gear when the bike lost power and a chimps tea party began under my arse. Limped home, dropped the oil and lots of tiny filings on the magnet, a few in the gauze filter and more in the paper filter. Off with the rocker cover and soon evident that the inlet rocker bearing had disintegrated, all the little needle rollers had gone and instead of having 0.1 mm of clearance I now have 5mm. Thanks to this site I knew what had happened straight away having read posts previously about bearing failure.
My concern now is where have all the bits gone and what to replace.
Should I buy a new rocker arm or attempt to replace the bearing?
Should I just flush the engine then fill with oil and do a few very early oil changes or is there anything I should strip and look for?
Is it possible there could be a few complete needle rollers floating around or are they generally ground up?
Any input from those of you who have experienced this would be appreciated.

Cheers folks.

Cheers chaps. I'm tempted to go for just the followers as plumbob says, seems an easy job and the rockers are good so seems a shame to bin them. On closer inspection of the bearings I think they may have been breaking up for some time, there are a few flat spots on the outer bearing where it touches the cam lobe, cam seems to have coped ok though with no nasty scores etc. Can't believe it actually ran with 5mm gap on the inlet valves!

Cheers Taffy, will flush the engine with petrol and remove clutch cover to check they're not lurking in there, let you know how it goes when I reassemble next weekend.

Hi all, got the bike back together today. Replaced cam follower bearing on the inlet rocker, straight forward job of pressing the old one out and the new one in. Off with the clutch cover to gather all the needle rollers from inside and flushed out with petrol, luckily no further damage seems to have been done. Set the valves using 1/6 turn method which is much easier to do with the radiator out of the way. Had a little water leak from the pump weep hole which seems to have stopped now. Moved the kick start round one spline whilst putting back together which is an improvement, you get a much better swing. I think this bearing has been on it's way out for some time because the engine sounds so much better, no more rattles which I thought were normal on Bergs, really does sound smooth. Starting is a doddle now, 1st kick every time, even cold. Amazing difference on performance too, smoother, far more responsive low down and generally just faster and nicer to ride. Wasn't too expensive to carry out either, just over Ł50 for bearing, gaskets and oil and a days tinkering from me.
As for what caused the bearing to fail, valve clearances to tight I reckon. When I first joined this site I saw countless references to valve clearances and that they should be checked religiously, it's true gents, go check em!

Exhaust bearing was fine Bobzilla, cleaned and no play at all. I was going to replace both until I spoke to Dave Clarke Racing who suggested if the other was fine then leave it, appreciate your point though.