Yigler's page

You also have to keep in mind that as a creatures size category goes up in size so does their carry capacity making it perfectly feasible for a colossal creature to be wielding a greatsword that weighs approximately 980lbs. This also makes it nearly impossible and highly improbable for a medium creature to wield such a monstrosity.

The carry capacity bonuses go by~

~Biped~
Large x2
Huge x4
Gargantuan x8
Colossal x16

~Quadrupedal~
Large x3
Huge x6
Gargantuan x12
Colossal x24

So a medium Creature with a 21 str can carry 153lbs. light load
Where a colossal Creature with a 21 Str can carry 2448lbs. light load

and seeing as most colossal creature have a Much Higher str than 21 (generally between 40-50) we can assume they could wield such weapons and any armor with ease but makes it completely ridiculous for standard medium creature to try to.

So even going by armor values if we apply the same multipliers of

Large x2
Huge x6
Gargantuan x24
Colossal x120

Then a standard colossal biped wielding a greatsword and full plate would come in with approximate totals of 6960lbs. for just the two.
But at just 30str, a colossal creature can carry over 8500lbs of stuff while remaining within the light load limits.

But i too have searched through and found nothing to support what i chose to do with the weight value of weapons and gear in my games.

Actually after having this conversation with my DM I finally figured it out when I looked at different appropriately sized weapons. It does scale drastically on weapons though so beware. Every time the size category increases you simply multiply the new eight by an extra +1. This means when you go to large the weight is simply doubled. However when you increase the size again to huge multiply the new weight by 3. And then again when you increase the size to Gargantuan multiply the new weight by 4. In the end this translates into a base weight multiplication of

Large x2
Huge x6
Gargantuan x24
Colossal x120

Thus making it almost impossible for a medium creature to wield a Colossal weapon without the correct magical effects.