TL; DR - Det finns inget öppet speciellt om Hagrids trollstav. Han skulle ha köpt hos Ollivander butik precis som någon häxa eller trollkarl skulle.
1) Herr Garrick Ollivander på Wand Längd: Från JK Rowling personligt skrivande (canon) :
Most wands will be in the range of between nine and fourteen inches. While I have sold extremely short wands (eight inches and under) and very long wands (over fifteen inches), these are exceptionally rare. In the latter case, a physical peculiarity demanded the excessive wand length.
Så, en speciell trollstav kan göras om det behövs för en trollkarl med onormala proportioner .
2) Hagrids tavla beskrivning av HP Wiki (inte kanon) :
The wand of Rubeus Hagrid is 16" long, and made of oak wood; the core material is unknown. This wand is the longest ever recorded, except for Lucius Malfoy's wand, which measured 18" in length. The wand is described as "rather bendy". This wand was snapped when Hagrid was expelled from Hogwarts School of Witchcraft and Wizardry in his third year, and either repaired or replaced at some point prior to his picking up Harry at his eleventh birthday. The wand was presumably concealed inside an umbrella.
Här ser vi att Hagrids trollstav var längre än normalt men inte överdriven. T här är ingen anledning att tro att Ollivander inte skulle ha haft muren på lager.
Vi ser här att JK Rowling säger att en av de längsta wandsna var 15 "men att Hagrids var 16" och Lucius "var 18" ... HP Wiki är inte 100% korrekt, det är inte en källa för Canon på detta webbplatsen. Ännu fortfarande kan canoncitationstecknet Ollivander göra en anpassad tavla om det behövs.
3) Väggar brukade vara skräddarsydda från JK Rowling-skrivandet på Mr. Ollivander (canon) :
Prior to Mr Ollivander's proprietorship of the family business, wizards used a wide variety of wand cores. A customer would often present the wandmaker with a magical substance to which they were attached, or had inherited, or by which their family swore (hinted at by the core of Fleur Delacour's wand). Mr Ollivander, however, was a purist who insisted that the best wands would never be produced merely by encasing the whiskers of a favourite Kneazle (or the stalk of a Dittany plant that once saved a wizard's father from poisoning, or the mane of a kelpie a witch had once met on holiday in Scotland) in the customer's favourite wood. The best wands, he believed, had cores of immensely powerful magical substances, which were expertly enclosed in specially selected and complementary wandwoods, the result to be matched to an owner with whom the wand itself felt the most affinity. While there was initially substantial resistance to this revolutionary way of crafting wands, it swiftly became clear that Ollivander wands were infinitely superior to anything that had come before. His methods of locating wand woods and core substances marrying them together and matching them to ideal owners are all jealously guarded secrets that were coveted by rival wandmakers.
Här ser vi trollkarlar kan ta med egna material för att göra en tavla om allt annat misslyckas.