How to simulate hyper-spectral images
The spectrum of an object is typically a product of the spectrum of the light coming from a light source and the reflectance spectrum of the object. For visible light, I have an old collection of both of those, in the data.txt file in this jar archive. For example:

canvas;
number=1067;
category="food";
name="wheat bread crust";
reference="Eastman Kodak (Ron Gershon)";
start=390;
step=2;
evendata=0.0465, 0.0470, 0.0446, 0.0444, 0.0443, 0.0440, 0.0435, 0.0433,
0.0435, 0.0433, 0.0432, 0.0431, 0.0442, 0.0435, 0.0438, 0.0444,
0.0446, 0.0449, 0.0454, 0.0459, 0.0464, 0.0467, 0.0467, 0.0469,
0.0476, 0.0479, 0.0487, 0.0490, 0.0496, 0.0502, 0.0507, 0.0511,
0.0515, 0.0521, 0.0527, 0.0532, 0.0542, 0.0550, 0.0557, 0.0567,
0.0576, 0.0584, 0.0592, 0.0603, 0.0612, 0.0622, 0.0631, 0.0637,
0.0657, 0.0666, 0.0677, 0.0690, 0.0703, 0.0719, 0.0730, 0.0744,
0.0763, 0.0778, 0.0802, 0.0813, 0.0823, 0.0845, 0.0861, 0.0874,
0.0906, 0.0921, 0.0940, 0.0961, 0.0979, 0.1001, 0.1026, 0.1047,
0.1071, 0.1094, 0.1116, 0.1140, 0.1165, 0.1192, 0.1222, 0.1248,
0.1272, 0.1302, 0.1327, 0.1357, 0.1387, 0.1413, 0.1443, 0.1478,
0.1507, 0.1540, 0.1573, 0.1600, 0.1632, 0.1667, 0.1699, 0.1735,
0.1768, 0.1799, 0.1834, 0.1872, 0.1906, 0.1949, 0.1983, 0.2021,
0.2062, 0.2104, 0.2143, 0.2184, 0.2228, 0.2266, 0.2306, 0.2343,
0.2391, 0.2432, 0.2472, 0.2518, 0.2557, 0.2597, 0.2646, 0.2688,
0.2732, 0.2779, 0.2818, 0.2861, 0.2909, 0.2952, 0.2997, 0.3045,
0.3086, 0.3124, 0.3171, 0.3220, 0.3259, 0.3306, 0.3349, 0.3390,
0.3441, 0.3483, 0.3528, 0.3574, 0.3624, 0.3667, 0.3716, 0.3766,
0.3811, 0.3863, 0.3908, 0.3954, 0.4011, 0.4058, 0.4105, 0.4162,
0.4204, 0.4249, 0.4299, 0.4350, 0.4404, 0.4455, 0.4495, 0.4543,
0.4589, 0.4631, 0.4684, 0.4724, 0.4764, 0.4818, 0.4864, 0.4906,
0.4958, 0.4989, 0.5037;


The spectrum is evenly sampled at 2 nm ascending steps starting at 390 nm. It is actually absorbance data which you need to convert to reflectance by:

$$\text{reflectance}(\text{wavelength}) = 10^{\text{-absorbance}(\text{wavelength})}.$$

For a light source, a common choice is CIE D65. Its power spectrum in 10 nm bands starting at 300 nm is:

0.0341, 3.2945, 20.236, 37.0535, 39.9488, 44.9117, 46.6383, 52.0891,
49.9755, 54.6482, 82.7549, 91.486, 93.4318, 86.6823, 104.865,
117.008, 117.812, 114.861, 115.923, 108.811, 109.354, 107.802,
104.79, 107.689, 104.405, 104.046, 100, 96.3342, 95.788, 88.6856,
90.0062, 89.5991, 87.6987, 83.2886, 83.6992, 80.0268, 80.2146,
82.2778, 78.2842, 69.7213, 71.6091, 74.349, 61.604, 69.8856, 75.087,
63.5927, 46.4182, 66.8054, 63.3828, 64.304, 59.4519, 51.959, 57.4406,
60.3125