I have some changes I make to standard D&D equipment.
Slings should have a better range than the rules say. I change it so that when using a cast bullet, designed for usage in a sling, the range is the same as that of a shortbow. I believe the evidence shows that as a valid correction. When using a found stone, the distance is half of that of a shortbow, due to the random characteristics of the rock.
Foraging for stones, when the terrain makes it possible, requires a successful investigation roll. If successful, one stone per point above the DC per minute spent is retrieved. In most situations the DC would be very low, indicating a high probability of finding suitable stones.
Sling Bullet Molding Set: Costs 1 GP, weighs 2 lbs, comes with a 5-bullet mold, a ladle for pouring the molten metal, and a small pot to melt the metal in. One lead bar (2 CP, 1.5 lbs) can make 20 bullets in 10 minutes. Silver bullets can be made at a cost of 4 SP per bullet.
A competent blacksmith can make a bullet molding set in a day. A business-savvy blacksmith could do it in a few hours for a higher price.
Note: 1.5 lbs (the weight of 20 lead bullets) is 24 oz. Coins are typically 1/3 oz, so each bullet (1.2 oz) takes 4 coins' worth of metal.
Lead and tin can be melted in a typical wood fire. Other metals like iron, steel, silver, and gold must be melted in a forge.
Wielding a spear two-handed adds the Reach property. This better reflects the reality of using a spear to control the area around the user.
Cost: 10 SP per spear. Time: 50 spears/week. A single spear takes a couple of hours. If two characters work on separate parts, time is halved.
If no forge is available, quadruple the crafting time due to building and using a crude forge.
Most Norse would use a seax rather than a Roman-style short sword. In D&D terms, treat it mechanically as a short sword. Single-edged, utilitarian, and common in Scandinavia.
The swords used by Vikings would be classified as longswords in D&D but are not long enough for two-handed use.
Boss-grip round shields were standard. Lightweight, versatile, and easily replaced — but not very durable.
Widespread and cheap. Often called a Gambeson in later France. In the early Viking age, it might be called a Kaftan or vápntreyja.
Most Viking-age people were simple farmers. Even raiders farmed much of the year. Wealth and resources were scarce, especially in the early Viking age.
Custom backgrounds are available and preferred for historical flavor. Starting gear should reflect this.
Most standard D&D classes can be justified, though some fit better than others.
Playable races in the real world = humans. But for kid-friendly games, elves, dwarves, tieflings, dragonborn, and warforged are allowed.
A typical Scandinavian might wear:
Clothing lacked pockets and buttons. Small pouches were worn on belts.
Some things are not allowed unless very well justified:
Some gear (like crossbows) is not available at character creation, but might be found through gameplay. Crossbows were known but rarely used in Scandinavia.