I can tell you buying a camera bag is like going through school. You start off kindergarten style, then progress to uni.
If you really want to buy 1 bag, you will need to sit down and spend some time thinking it out.
Most decent sized camera bag will be able to put all those small items you mentioned so they are not so impt.
What you really need to consider is
1) how much gear you have now, how much gear you might have in 3 years time or more.
Just the size of your body will determine which kind of bag you cannot use (body+grip makes it much taller)
2) how much traveling will you be doing with this bag. as in not just outing in spore, but like overseas trips etc.
3) do you need it to fit a laptop? if yes, how big is your laptop? 10inch netbooks? or 14inch-15inch laptop?
4) do you do hikes? in weather changing conditions?
2+3+4 will tell you to look for bags that can either carry laptops, carry additional clothings or materials like raincoat, waterbottles, etc
4) Your kind of photography. street? beach? need fast access? security? wet and wild weather (eg shooting storms etc)
Your duration of photography
5) your personality: you want vibrant hip stuff like crumpler? stylish stuff like the bilinghams? or you want low profile eg just a black bag?
Once you have thought these through, go online and do more studying. visit websites for camera bags:
Typical: lowepro, tamracs, kata, Think tank, crumpler, etc etc.. there are also a fair number of brands that may not be so well known but can have some nice tricks.
look for bags that have a rain sleeve. Most backpacks/sling bags should have.
Then if you want cheaper, you may be able to find some imitations from HK or China on fleabay. I would say they work pretty much the same, maybe even better functions such as the placing of the tripod holder.
1) In my case, i started off with a small sling/shoulder bag that can hold 1body+lens and some small accessories.
2) Then lens grew bigger.. so got a back sling bag.
this one can carry 1 body+ small sized short tele, plus either a 50mm and a sb600, or another lens eg a 85mm if I am not carrying the sb600.
Then came the battery grip.
I can modify the set up to carry body and lens dismantled on the above bag.. but very annoying..
3) so bag upgrade again
this time a tamrac sling bag. This one can carry body+grip+80-200mm attach.. it is a top loader style, and can add 2 more lenses + flashes. and small accessories.
this is fantastic for me for use under 4hrs. if more the shoulder can become really sore.
but access to lenses etc is really fast.
4) THen I started to travel more between states (i am based in australia now)
and brings a laptop.. so I went with a kata 467.
pretty good.
I can carry laptop, camera compartment can carry: 1body+grip+short tele, + 2 lens+ small accessories. the upper compartment can either carry my clothings+food, or more camera gear like 80-200, + 2 flashes etc.
5) Then I started a bit of event work. so found these bags too annoying. the sling bag can swing ard. so I got the lowepro belt system. very good for event photography.
6) eventually, equipment grew too much, and i upgraded to the lowepro computrekker (medium size i think). This bag is like a wormhole hehehehe.
did I throw away or sell off or abandon other older bags?
nope they are all still being used!!... maybe not number 1.
when i do street photography, I tend to go
bag 3) for new places,
bag 2) for revisits, and to limit lenses and improve creativity
Beach photography
bag 3)
events:
Bag 6) plus bag 5)
interstates events: Bag 4/6 plus bag 5, depending on how much gear i need.
Hope that helps
